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The /974 Distinguished Lectureship in Materials and Society

Metallurgy as a Human Experience

CYRIL STANLEY SMITH

The ent i re h i s to ry of mater ia l s i s examined w i th emphas is upon the s t ruc tura l d i f fe rences at s tages of d i scovery , deve lopment and mature ad jus tment in ana logy w i th the S -curve o f a phase change . The ear l ies t d i scovery of a lmost a l l use fu l mater ia l s o r techn iques oc - cur red in mak ing decorat ive ob jec ts . A l loy ing , shap ing and we ld ing techn iques began in jewe l ry and scu lp ture ; c rys ta l l i za t ion , sp inoda l t rans format ion , and in ter face energy equ i - l i b r /um were sens i t ive ly used in ceramic g lazes ; o r ienta l l acquer and ce l lu lo id t r inkets a re precursors of the p las t i c indust ry . Far f rom be ing an app l ied sc ience , p rac t i ce in mater ia l s was fa r in advance of phys ica l and chemica l theory unt i l l ess than a century ago , and even today in tu i t i ve unders tand ing cannot be d i s regarded . The a lchemis ts bu i l t the i r myst i c concepts upon the co lo r ing techn iques of anc ient a r t i sans . Chemis t ry came f rom dy ing , pot mak ing and par t i cu la r ly the quant i ta t ive separatory react ions of the as - sayer . But , once deve loped , sc ience became h igh ly e f fec t ive in cont ro l l ing and improv ing indust r ia l p rac t i ce . The d i scovery of e lec t r i c i ty gave a new type of p roper ty to be s tud ied , and the r i chness of today 's approach to mater ia l s came f rom the subsequent jo in ing of the phys ic i s t ' s approach w i th the o ther th reads that had been matur ing th rough the ages . Tech- no log ica l change a l te rs the pat te rns of human in teract ion and it under l ies most soc ia l up - heava ls . Techno logy i s a r i ch par t of the human exper ience and it deserves fa r more a t - tent ion than i t has h i ther to rece ived by h i s to r ians .

Dr, Cyril Stanley Smith came to the United States from England in 1924, following his graduation from the University of Birmingham. He took his graduate work at Massachusetts Institute of Technology. In 1927 he joined the metallurgical staff of American Brass Company and organized a research department which provided the tonic that was needed by the brass indust,;y at ~at time.

As an avocation he translated, in collaboration with Martha Teach Gnudi, the Italian foundryman Biringuccio's "Pirotechnia," a work antedating Agricola and mote original.

In 1942 Dr. Smith went to Washington as research supervisor of the War Metal- lurgy Committee. In 1943 he went to the newly forming Los Alamos Laboratory of the Manhattan District, to take charge of the metallurgical end of designing and building the atomic bomb.

Dr. Smith left Los Alarnos at the beginning of 1946 to found the Institute for the Study of Metals at the University of Chicago and to serve as its Director and Professor of Metallurgy, Under his leadership this Institute became one of the outstanding research organizations of the nation. His researches on intercrystalline interfaces and the influence of interface energy and topology on the structure of polycrystalline materials have become an essential part of the science of metallography.

Dr. Smith returned to MIT as art Institute Professor in 1961. His joint appoint- ment in the Metallurgy and Humanities Departments reflected the basic change in direction his research was to take. His Professorship of the History of Technology and Science expressed the cutm~at~on of a long and deep commitment to the humanistic aspects of technology and he was being recognized not only as a distinguished metallurgist but as an historian, and, above all, as a humanist. His most important contribution to the history of technology from the point of view of his students and colleagues has beer~ his insistence upon understanding technologies from the inside, not by reading about them but by becoming immersed in the materials and processes that make them what they are.

At MIT, Dr. Smith founded the Labocatory for Research on Archaeological Materials where archaeologists and materials scientists can study the technologies of ancient societies through the examination of their material remains. His unique ability to blend a deep appreciation for the aesthetic side of man, an historian's insight into the way in which technologies unfold, and a scientists's delight ha the structure and properties of materials have inspired all those who have had the good fortune to work closely with him. Dr. Smith is now Emeritus Professor, Massachusetts Institute of Technology.

METALLURGICAL TRANSACTIONS A VOLUME 6A, APRIL 1975-603

IN this lecture I propose rather hasti ly to survey the ways in which mater ia ls have histor ical ly interacted with human behavior and social s t ructures. The theme is a complex one, involving everything from an indi- v idual 's using his hands to make some thing of beauty or util ity, his growing intel lectual order ing of the world about him, and the use of mater ia ls in the communication of ideas, as the basis of commerce, and in the en- v i ronment which sustains life and society.

Because of the inconspicuous ubiquity of mater ia ls and the constancy of their individual propert ies they serve as a fine touchstone to reveal man's individual and social character is t ics . Nothing can be more human than taking delight in an object such as a blue stone or a bit of mal leable polishable red native copper, or than the intel lectual feat of establ ishing a re - lation between the two via pyroteehnology, or than, in a different sphere, exchanging the pract ical results of this knowledge for food and so providing another basis for social cohesion.

The long sweep of mater ia l history begins with the discovery of the existence of useful propert ies, which involves art ; then the production of things in quanti- t ies to match known needs, which requires industr ia l and social organization of different types at different t imes; and, very recently, the development of a science that permits the selection of a chemical composit ion and the manipulat ion of s t ructure at many levels in o r - der to achieve an optimal balance of those propert ies that are required in any part icu lar application.

In only a smal l part of h istory has industry been helped by science. The development of a suitable sc i - ence began when chemists put into rat ional order facts that had been discovered long before by people who en- joyed empir ica l d iverse experiment. The change to an essent ia l ly atomist ic physical approach, so productive in the present century, has left untouched many problems too complex for dissection, and one can see in the work of today's mater ia ls engineers a trend toward a conscious appreciation of the need of an ecological balance between many different motivations and slants of mind.

I shall say l itt le about the industr ia l and commercial sides of the field, not because I underest imate their essent ia l and dominant role throughout history as in the present world, but because other lecturers in this ser ies 1 have dealt with these aspects far more authoritat ively than I can, and because my natural sympathies are with the tentative beginnings of new viewpoints rather than with their tr iumphant success.

My appreciation of the honor in being asked to ad- dress this joint meeting of the metal lurgical societ ies of the United States is heightened by the recol lect ion that it is exactly fifty years ago that, as a naive student immigrant , I attended, in Boston, my f i rst meeting of the American Society for Steel Treating, as the ASM was then called. This society and the AIME together have provided most of my professional insp i ra - t ion as I moved from academic to industr ia l science and back to academia after a taste of governmental involvement. What a hal f -century this has been! As an undergraduate I had to decide whether to enrol l as a ferrous or a nonferrous metal lurg ist ; I heard little about ceramics and nothing whatever about polymers. The curr icu lum, though ref ined in detail, had pretty much the same aim as the eighteenth century courses

604-VOLUME 6A, APRIL 1975

in the mining academy in Fre iberg and the l~cole des Mines in Par is . Today's student may call h imself a scient ist or an engineer, but he is always a l itt le of both, and he is introduced to all mater ia ls compara- tively. In histor ical perspect ive one can see that the recent changes are s imply a resul t of the coming together of s t reams of human experience, both pract ical and intel lectual, that have been matur ing independently of each other for a very long t ime.

Profess ional ism in mater ia ls , until very recently, meant faci l i tating and cheapening the large scale production of one or another of them. Yet, it all started mi l lenia ago with an interest in the propert ies of mater ia ls without regard to their type, and the recent shift of the center of scientif ic interest to propert ies is a natural return. Which is not to say that the or - ganized search for raw mater ia ls and efficient ways of getting them to the user is not just as important as it ever has been.

During the last three thousand years a re lat ively few genera l -purpose mater ia ls served near ly all appl ications. Materials of general types used today (except in electronic applications) were discovered well before 1000 B.C. A few composit ions in each class were selected, and they were those that were insens i - tive to abuse in both fabricat ion and in service. They functioned well enough to be largely taken for granted and the challenging problems lay in cheapening them and extending the scale of their manufacture. In the ent i re period from Classical t imes to the end of the nineteenth century innovation in mater ia ls lay mainly in production and in application. The only novelty as far as propert ies were concerned lay in the standardi - zation and pract ical control of their composit ion and treatment, and in the fact that the well-known reac - tions and propert ies served repeatedly to incite advances in scientif ic theory. At least in our area, sc i - ence arose from a prehistory in pract ice far more often than pract ice benefited from the application of theory. The future will be different. [But we should not overlook that meanings of words change with time, and the human activity that today we isolate and call science found different outlets in ear l ie r t imes. The alert empir ica l exper imenter who, for example, d is - covered the f i rst useful alloy (of copper and arsenic) and used it to cast a smal l statuette to delight his over lord perhaps has as much claim to be called a scient ist as the modern theor ist who elucidates the band structure of alloys and uses it to get academic promotion! ]

Most discover ies have been made in rea l systems, not the idealized ones of exact theory. With very few but staggeringly important exceptions, science has been the explanation of things already known. Of course, when the explanation is on a basic enough level to reveal the common factors in diverse s i tua- tions, it is enormously helpful to the pract ical man in ref ining and control l ing his operations. The few var i - eties of iron and steel of empir ica l days could not have become the near ly 300 var iet ies of SAE steels without control based on both chemical and physical concepts. This indeed is applied science. It is a prerequis i te of the social usefulness of our profession, but it is not the way to new knowledge. The popular impress ion of "pure" science discovering things that are elaborated and put to practice is, to my mind, very ra re ly true.

METALLURGICAL TRANSACTIONS A

Discovery is quite different from understanding. A good theory, indeed, tends to close rather than to open the mind to unexpected phenomena. Science is much more than discovery, and so is pract ice.

THE STRUCTURE OF CHANGE

Much of the interest in our profession l ies in the interplay of levels. Certainly, some fami l iar i ty with atomic nuclei and electrons is needed, but, since mater ia ls make all things possible, men with knowledge of both old and new and possible mater ia ls are also in contact with the most important social problems at any period. Int imately so in relat ion to warfare, travel , communicat ion and the like, more per ipheral ly so in pol i t ics--but consider the importance of raw mater ia ls and of refuse in world and urban polit ics, and even the role of str ips of polymer impregnated with magnetic part ic les in recent American constitutional debates. There is no lack of pert inence at any level between interatomic forces and global affairs. Mate- r ia ls are indeed the enablers of everything, like the electron itself but operat ing at a level that is more complexly structured.

Though any one man by the l imitat ions of his nature or his opportunit ies must perforce ignore most of what mankind as a whole knows--and, indeed, he must special ize if he is to be at all effective in his work-- he misses much if he is not at the same t ime aware of things beyond the boundaries of his specia l ism. This sure ly is the meaning of the report of the recent Academy of Sciences' COSMAT committee 2 under the chairmanship of Professor Morr is Cohen. With all the difficulty that the committee evidently had in de- f ining its l imits , there rea l ly is a field of "Mater ia ls Science and Engineer ing" .

A connected field, sc ience and engineer ing; more - over- -and this is new--a field encompassing all mate~ r ia ls within its boundaries. Such general i ty would have been unworkable not long ago, but, because of science, deep special izat ion can now be achieved without loss of sight of broader interconnectedness within a f ramework that overemphasizes neither science nor pract ice to the exclusion of the other. We now have most of the br icks we need and can start the construc- tion of an master edifice with communicat ing cor r i - dors and with communal work space to replace the individual huts in which we have separately l ived in the past.

Everyone has heard of the concept of the Ages of Man based upon mater ia ls : the Golden and Silver Ages of the Greeks; the Stone, Bronze and Iron Ages of the archaeologist. (Oddly, these classi f icat ions do not in- clude, as they should, a ceramic age; and one has to move to the Chinese phi losopher's five e lements for any scholar ly acknowledgment of the role of natural organic polymers, the use of which presumably pre - ceded shaped stone.) Best known, perhaps, of all cases in which mater ia ls have enabled or even precipitated social change is the use of metals in warfare. But mater ia ls also affect the way men think. Not only via spectaculars such as the recent moon landings, which cannot help but change man's view of himself as pro- foundly as did the conceptual sun-centered astronomy of Copernicus, but also through the mater ia ls with which an art ist works, or the pen and brush, the clay,


papyrus, vel lum, paper, inks and type metal which so great ly enlarged communicat ion before sol id-state semiconductors part ly took over. Every one of these had a vital role in history and every one was the re - sult of imaginative empir ica l selection and laborious development.

These and hundreds more mater ia ls and uses grew symbiot ical ly through history, in a manner somewhat analogous to the S-curve of a phase t ransformat ion in the mater ia ls themselves. There was the stage, inv is- ible except in retrospect , wherein f luctuations from the s ta tus quo involving only smal l local ized distort ion began to interact and consolidate into a new structure: this nucleus then grew in a more or less constant en- v i ronment at an increasing rate because of the increas - ing interfacial opportunity, unti l f inal ly its growth was slowed and stopped either by depletion of mater ia l necessary for growth, or by the growing counter -pressure of other aspects of the environment. Any change in conditions (thermodynamic = social) may provide an opportunity for a new phase. We all know how the superpos i - tion of many smal l sequential S -curves themselves tend to add up the giant S-curve of that new and larger structure which we call civi l ization, and we are beginning to wonder what new st ructure can be nucleated to prevent decay. The terminat ion of one S-curve marks the l imit of growth of one idea or s t ructure; the continuation of the envelope marks the growth of a superst ructure , incorporat ing and modi- fying the previous stages within a larger organization. Because at any one t ime there are many overlapping competing subsystems at different stages of matur i ty but each continual ly changing the environment of the others, it is often hard to see what is going on. More- over, nucleation must in principle be invisible, for the germs of the future take their val idity only from and in a larger system that has yet to exist. They are at f i rs t indist inguishable from mere foolish f luctuations destined to be erased. They begin in opposition to their environment, but on reaching matur i ty they form the new environment by the balance of their multiple interact ions. This change of scale and interface with t ime, of radical misf it turning into conservat ive in ter - lock, is the essence of the history of anything whatever, mater ia l , intel lectual or social. Our professional job as engineers is mainly to faci l i tate the stage of growth, where ends and means are both v i s - ible, if indist inctly.

The "new level of s t ruc ture , " so often re fer red to, is rea l ly the discovery of a new interdependence between parts, which requires a means of communication having a complexity commensurate with that of the parts. The unity should not be called a synthesis; no useful s t ructure resul ts from putting together un- changing parts: each part is influenced by its neigh- bors and all parts change as the new structure finds its own val idity through these interact ions.

DISCOVERY IN ART

The history of mater ia ls shows this pattern of complex growth. The ear l iest records of man are tools crudely fashioned from stone. These tools, of course, represent only the undecayable parts of the matter that he util ized. I would like to believe that the f i rst move toward civi l ization was a genetic mutation that en-

VOLUME 6A, APRIL 1975-605

hanced man's capacity for sharing the enjoyment of his environment, and the active cur iosity that this en- gendered. The ear l iest archaeological evidence for the intentional modification of the propert ies of matter - - the hardening of clay by f i re- - is not a useful tool or weapon but a smal l statuette, the "Venus" of Ves- troniee. (Fig. 1) Thereafter the f irst appearance of almost all art i f ic ial mater ia ls and of t reatments to ad- just their propert ies or shapes to specific uses appear f i rst in objects of art, or at least in objects of cere- mony in which uti l ity res ides in their aesthetic over- tones. This pers is ts well into the 19th century, when art for the masses continued to inspire many new fabricat ion techniques.

Until very recent ly people doing the ser ious work of the world have not experimented but have used only methods of establ ished rel iabi l i ty. Discovery is less l ikely to occur when people are desperately earnest than when they are in a sensit ive, somewhat playful, mood. The ar t i s t ' s sensit iv i ty to color and texture natural ly br ings him into contact with more proper- t ies of mater ia ls than are encountered by the maker of useful objects. I have elaborated this viewpoint in other papers; 3 here let me simply i l lustrate the theme by mentioning evidence for the appreciation, if not sc i - entific understanding, of some rather subtle aspects of mater ia ls many centur ies ago.

Fig. 2 shows one of the very ear l iest metal art i facts known, a smal l pendant using the mal leabi l i ty of native copper and, of course, its optical propert ies. Most of metal lurgy, both alloying and heat t reatment as well as mechanical shaping, began in jewelry. The bull f rom Horoztepe (Fig. 3) shows good casting technique (probably lost-wax) but is especial ly interest ing because of the white decorative bands which are of the interme- tal l ic compound Cu3As produced by a cementat ion-di f - fusion react ion at about 400~ Diffusion is also involved in the famous red and black Greek pottery (Fig. 4), for both colors are due to iron in the very fine grained clay that was used, and both were black during the f i rst stage of f i r ing in a reducing atmo- sphere, but the black parts were applied in a clay that contained a smal l addition of alkali and so, when the f i r ing ended under oxidizing conditions, the diffusion of oxygen that caused reddening oxidation elsewhere was locally delayed in the more vitreous substance.

True vitreous si l icate mater ia ls had been made as glazes 4000 years before this, at f i rst by a kind of cementation react ion between s i l ica and plant-ash alkali, and, later, by premixing the powdered components of a si l icate glass. Thereafter innumerable colors were achieved by additions to the glaze of heavy metal oxides, (sometimes precipitated in uniform colloidal d is - pers ion by spinodal t ransformat ion) while a host of decorative textures were produced by the nucleafion and growth of crysta ls as well as by local modification of surface contours though the effects of surface ten- sion and viscosity. Though most of these techniques began in the Middle East, ceramic ingenuity and beauty reached an apex in Sung China. When later Chinese and Japanese ware was imported into Europe it inspired intense chemical and pyrotechnological experiment (Fig. 5). Glass as an independent substance came out of glaze in the third mi l len ium B.C., and the temperature /v iscos i ty character is t ics of amorphous mater ia ls were f i rst used during the f i rst century


B.C., in making blown glass vessels . Strong mater i - als depending on the formation of hydrated crystals from pref i red calcareous rock, as in a modern ce- ment, goes back to the decorative uses of plaster in f loors and sculpture in the ninth mi l len ium B.C.

The superb heroic size statue of Poseidon (Fig. 6) would have not been possible had not the founders discovered how to make strong welds, invisible after finishing, by running in molten bronze to fuse and join the edges of previously-cast pieces of smaller size (Fig. 6(a)). The properties of cross-linked organic polymers were used as a kind of paint early in the Shang dynasty in China, and in thicker richer lacquer ware by about 300 B.C. (Fig. 7).

Beyond question, the most skilled manipulation of steel under the hammer as well as control of carbon content, grain size and hardening of steel under dif- ferential cooling rates was that of the Japanese sword- smith, which reached its apex in the thirteenth to four- teenth centuries A.D. (Fig. 8).

THE BEGINNINGS OF A SCIENCE OF MATERIALS

The artist is not conspicuous in materials development today: indeed he is far more likely to ask the materials man for new substances to work with than to give them. Discovery will continue to be motivated by an essentially aesthetic curiosity, but those doing it have moved from studio to laboratory. Perhaps the greatest change lies in the patrons of discovery, for their motives are no longer aesthetic, but are related to profit, prestige or national security.

But discovery is only one aspect of man's interaction with materials. The materials profession has been totally changed in the last half-century by the scientific framework within which materials are un- derstood. This strand of the story has two threads both of which lead back to the opposing schools of Greek philosophy in the fifth century B.C.--the emphasis on mathematical form and structure on the one hand, or on more sensual tangible properties on the other. Both have practical roots in workshop practice. To read Ar istot le 's account of matter in the Meteoro- logica is to walk with him through the ar t i sans ' quarters , noting strength and weakness, plast ic ity and br i t - t leness, the influence of heat in soaking, boil ing and melt ing operations, and the greater violence of the meta lsmith 's f ire. One can see in his famous four e lements- -earth, water, air and f i re- - the basic states of matter, solid, l iquid and gas, which he supposed to be var ious ly combined with energy to give the wonderful d ivers i ty of mater ia l propert ies. Democritus before him must have been aware of the ar t i san 's f rac- ture test which made vis ible the var iable granular i ty of mater ia ls , and he extended this granular i ty to the smal ler scale of atoms to account for everything. Both schools were on the right track, for mater ia l states and propert ies res ide in the arrangement and inter - action of atoms, but their reconci l iat ion was far in the future. Ar istot le 's e lemental qual it ies remained su- preme, almost unquestioned, until the seventeenth century when a reviving atomism became an important part of the new scientif ic attitude. However, the great advances that occurred around the mathematical methods of Galileo and Newton were in f ields wherein s t ruc -


ture was unimportant. The new corpuscular philosophy was not amenable to quantitative study and the physics of sol ids consisted only of mechanics (elast ic i ty and kinetics) until well into the present century.

MATERIALS, ALCHEMY, AND THE CHEMICAL REVOLUTION

Histor ical ly , though the revolut ion in chemist ry was delayed for a century after that in physics, in the sc i - entif ic approach to mater ia ls chemist ry was far ahead of physics. Basical ly important in turning chemical cur ios i ty into a science were the new cr i t ica l attitudes of mind, but no less important were social factors, es - pecial ly the new kinds of organizat ion of industry and commerce . The organization of great mining enter - pr i ses to exploit the extract ion of s i lver f rom copper by the ingenious l iquation process made accurate assaying inevitable. Rapidly expanding world t rade brought new natural and art i f ic ia l products for Euro- pean chemists to study, while the d iscovery of s i lver mines in the New World turned attention to a new met- a l lurgy using mercury , not f i re. Access to technologies that had developed in re lat ive independence in other parts of the world st imulated many changes in European philosophical, economic and social thought.

When the chemical revolut ion did come it was great ly dependent on the mater ia ls , techniques and apparatus of pract ica l metal workers and ceramis ts , as well as on the knowledge of the many phase separat ions used in smelt ing and ref ining metals, especia l ly as these

had been methodized and made quantitative by the as- sayers . The ear l ies t table of ordered chemical aff ini- t ies (Fig. 10) is mainly a graphic presentat ion of re -

Fig. 3--Cast bronze bull from Horoztepe, Anatolia. About 2100 B.C., Length 12.2 cm. The uncorroded silvery band of decoration is a copper-arsenic compound produced by a diffusion reaction at about 400~ Courtesy W. J. Young, Mu- seum of Fine Arts, Boston. For photomicrographs and dis- cussion see The Application of Science in the Examination of Works of Art, pp. 96-103, Boston 1973.

Fig. 2--Copper pendant from Shanidar Cave, Northeast Iraq. About 9500 B.C. Length 2.3 cm, thickness 0.3 cm. Shaped by hammering a piece of native metal and finishing with abrasives. (It is completely mineralized and there is a slight pos- sibility that it was originally simply carved from a lump of malachite.) Courtesy Professor Ralph S. Solecki.


Fig. 4--Greek amphora with red figures on black background, about 490 B.C. Height; 41.5 cm. Both colors are due to iron in fine-grained clay, but the black, being slightly vitrified, remained in a reduced state as the red responded to a final oxidizing stage during firing. Metropolitan Museum of Art, New York, 56.171.38.


Fig. 5--Porcelain cup of Japanese manufacture, (1700-1725, left) and a German copy (Meissen, 1730-1740). Much European research on mineralogy and high temperature chemistry was done before it was possible to duplicate the oriental ware. Courtesy Smithsonian Institution, Museum of History and Technology, Hans Sys Collection.

actions that were well known to the s ixteenth-century assayer in which immisc ib le liquid phases were formed and the part it ion of var ious metals between them quan- t i tat ively observed. The ancient process of cupellation made use of dif ferences in the oxidizabil ity of base and precious metals, the abil ity of molten lead oxide to d is- solve the oxides of most other metals, and the different interfacial energies of the products which enabled bone- ash to absorb the oxides so as to leave the metal as a clean near ly spherical bead. The purif icat ion of solid gold by hot cementation or by cold part ing was part icular ly subtle.

The assayer ' s knowledge of the constancy of some things remain ing unchanged through all these react ions made the concept of a chemical e lement eventually in- escapable. The metal lurg ist was completely fami l iar in pract ice with the role played by air in combustion

and in calcination, and he knew that gases were often evolved by the mixtures in his crucible. He even knew that calces (oxides) weighed more than the metals that gave r ise to them and to which they could revers ib ly be reduced. But the metal lurg ist did not put this into theory: it needed men of a different s lant of mind to see the underlying meaning, to perceive that something in air was as real a reactant as the metals themselves, and above all to regard pers istence through change as a basic principle.

It is interest ing to read the minutely descr ipt ive ac- counts by ear ly wr i ters on assay ing- -Lazarus Ercker (1574) is by far the best - -and to note the complete absence of any theory or even the apology for its absence which pract ica l wr i ters later felt compelled to make. Conversely it is interest ing to note the misuse of exper iment, though not its d isregard, by the theoret ical


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Fig. 6 - -The Pose idon of Ar temis ium, Bronze , 475 B.C. Los t - wax cast ing in severa l parts, jo ined by we lds produced by runn ing in meta l of the same compos i t ion as the original. 6(a). Detai l of we ld in leg of Pose idon . (Photo by Ar thur Steinberg). Cour tesy of Nat iona l Museum Athens .

wri ters of the t ime, the alchemists. Alchemy, the "Pre lude to Chemist ry , " as one of its leading students has called it, came to involve a wonderfully imaginative t reatment of mystic re lat ions between the grandest laws of the cosmos and an observed microcosm of color changes, phase separat ions and property changes of the kind long used by smiths, dyers and potters. Needham 4 has made the interest - ing dist inct ion between the aims of "aur i f ic t ion" and "aur i fact ion ," the former being the production of s imulated gold by var ious alloying, gilding or color- ing processes in the workshop and the latter the high

610-VOLUME 6A,APRIL 1975

aim of the alchemists, a fundamental t ransformat ion. He suggests that individuals concerned with the two approaches, being of different social c lasses, would have had little contact with each other, and that the ar t i san 's knowledge of how to make and how to detect f ictit ious or fraudulent gold need not have upset the di lettante phi losopher's conviction of the val idity of his aim or exper imental approach thereto. Even more recent ly we have heard it said that proof is not needed if the theory is r ight! All of this is a fascinat ing part of human history, part icu lar ly so when seen in re la - t ion to medicine in the global perspect ive that Needham provides, but I bel ieve that the contribution of alchemy to the later development of scientif ic metal lurgy has been overest imated. It was, it seems to me, not des- t ined to be an effective nucleus but was an interest ing f luctuation that failed to establ ish mutual ly re inforc ing interact ions with other knowledge. Despite their deep interest in manipulated changes in matter, the a lchemis ts ' overwhelming trust in theory blinded them to facts. The man who sees only a step toward the creat ion of gold in the yellowness that ar ises when copper is heated with calamine is no less near-s ighted than the pract ical man who sees brass only as a cheap and pretty alloy with which to make pots or shoebuckles. The pract ical man inevitably has a more accurate acquaintance with the real behavior of mater ia ls than anyone else and he cannot ignore things that he does not understand. Per - haps, even, the fact that he can work successful ly despite his lack of "sc ience" makes him less anxious to find a good theoret ical framework for his knowledge. It is the conscious and continuous interplay between theory and practice that makes science so powerful today. And one cannot but feel that s imi lar apprecia- tive relat ionships between cherished differences would be desirable in other social situations.

Everyone knows of the "Chemical Revolut ion" which came to a head in the work of Lavoisier. His redef in i - tion of the nature of a chemical element and the re - placement of phlogiston by minus-oxygen were not theoret ical insights obtained by meditation on the cosmos but were based direct ly upon new experiments with gases and the new understanding of compounds ar is ing from the new methods of analysis. 5 Two of Lavois ier 's col laborators in the famed Methode de Nomenclature Chemique of 1787 had, in the previous year, each independently advanced a phlogiston-free carbon theory of steel and had discussed its pract ical util ity. 6

Oxygen was discovered exactly two centur ies ago, and f ire became a chemical react ion between oxygen and carbon, in place of, or rather in addition to, its old role as a physical agency to promote change in other things. Though far less well known, the year 1774 also marks the f i rst signif icant return from the scientif ic chemist in exchange for the mass of factual information given him by the metal lurgist . This was the discovery of carbon in cast iron and steel.

Most alloys, of course, were obviously mixtures because the mixture of ingredients necessary to make them were known. Following Aristotle, however, steel had been widely believed to be a purer form of i ron-- natural ly enough since it resulted from prolonged heat- ing in a charcoal f ire, the purifying effect of which was universa l ly known. The smith knew how to manipulate iron in the f ire so as to obtain steel more or less con- s istently. In 1774, in Sweden, metal lurgist Sven Rinman,


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Fig. 7 - -Cranes and serpents , made of wood coated with lacquer. Height; 132 em. I l lust rates an ear ly use of a natural po lymer and its chemical stabil ity. Chinese, Warr ing States Period, 481-221 B.C. Courtesy of Cleveland Museum of Art, J. H. Wade Fund.


hav ing had h is mind sens i t i zed by recent chemica l s tud- ies of g raph i te by h i s fe l low count ryman C. W. Schee le , ident i f ied as a graph i te - l i ke mater ia I the res idue that fo rmed when cast i ron was d i sso lved in ac id . Seven years la ter th i s was conf i rmed by the great chemis t Bergman and h is s tudent Gadol in , s in a repor t g iv ing

quant i ta t ive ly the d i f fe rent amounts of carbon in the d i f fe rent qua l i t ies of i ron and s tee l , and a l so showing the presence of manganese , s i l i con , n icke l , and a "wh i te prec ip i ta te" la ter found to be a compound of phosphorus . In add i t ion they measured heats of reac - t ion and recorded the vo lumes of in f lammable a i r re -

Fig. 8--Sword made by Hiromitsu Sagami. Japanese, dated 1362 A.D. Detail, natural size. The texture resul ts from a com- pl icated forging regimen followed by quenching in water after an insulating coating had been locally applied to decrease the rate of cooling away from the edge. The final polishing with a graded ser ies of abras ive stones has revealed the intr icatedly patterned interface between hard and soft metal. The hardness of s imi lar swords is slightIy over 800 VHN at the edge, 200 to 300 in the body. Collection Dr. Walter A. Compton.

Fig. 9--Collection of objects molded of celluloid ( "Parkes ine" ) , the f i rst art i f ic ial polymeric mater ia l . Made between 1860 and 1866 by the inventor, Alexander Parkes, who is better known as a metal lurgist , they mark the very beginning of the great p las- t ics industry of today. Courtesy of The Science Museum, London. Crown Copyright.

612-VOLUME6A,APRIL 1975 METALLURGICAL TRANSACTIONS A

Fig. 10-Table of Chemical affinities. Etienne F ranco is Geoffroy: Mere. Acad. ScL, (Paris) 1718. Most of the react ions that are here put in signif icant symbol ic sequence had been used for some centur ies previously in metal lurg ica l separat ions and assaying.

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sult ing f rom solut ion of iron in acid, which they re - lated to phlogiston content - -cor rect ly so if phlogiston is regarded as the valence e lectron. Fig. 11 is the t i t le page of this most pregnant piece of meta l lu rg ica l l i te rature .

The new chemis t ry of Lavo is ier was square ly based upon Swedish analyt ica l chemist ry , which was then at the very foref ront of sc ience. New e lements were being d iscovered in minera ls , chemica l impur i t ies were found to be respons ib le for the good and bad qual i t ies of ores and products f rom dif ferent regions, and- -most important for us--the laboratory had been found to be of great uti l i ty to the smel ter , so br inging to bear on mater ia l s a di f ferent type of mind f rom that of the ancient pract i t ioners . It was the analyt ica l chemist who f i r s t brought sc ience to industry.

CERAMICS

It is instruct ive to compare the h is tory of the ceramic industry with that of meta ls . Subtle aspects of phys ica l and chemica l behavior were d iscovered by the potter before comparable d i scover ies in metals , and the benefits of chemica l analys is and contro l were also appl ied ear l ie r , but the eventual t rans i t ion to physics was delayed. The voluminous l i te ra ture of ceramics in art revea ls an apprec iat ion of the fact that technical factors under l ie the aesthet ic qual i t ies of var ious kinds of ware, and the techniques involved in the dupl icat ion of or ienta l porce la in in Europe ear ly in the eighteenth century have been extens ive ly studied by ar t h is tor ians , but the fact that Chinoiser ie was also a s ignif icant part of the h is tory of sc ience has been la rge ly over looked. Actual ly, the search for por - celain bodies and suitable g lazes and co lors provided a great st imulus to geology, minera logy, analyt ical

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METALLURGICAL TRANSACTIONS A VOLUME 6A, APRIL 1975 613

chemist ry and high temperature research. The production of porcelain attracted the lavish support of governments, albeit pr incely ones seeking prest ige as connoisseurs rather than national secur i ty or pros - perity. Ceramics also incited imaginative new forms of industr ia l organization, and recent histor ical studies suggest that the nucleus of England's economic growth may have lain as much in the pattern of Wedgwood's integrated sc ience-based market -or iented industry as it did in the better known contributions of Darby and Cort to iron manufacture or of Watt to power production.

The development of that marvelous mater ia l glass is equally part of our story. In its fabrication, in its propert ies, in its chemistry and structure as well as the uses to which it has been put, it has much in common with other products of pyrotechnology. 8 Scientif i - cally, the optical propert ies of glass have always been of major interest. The aesthetic delight in the color of medieval glass windows was paral le led by the intel lectual delight in the new world opened by glass pr i sms and by telescope and microscope lenses in the seventeenth century. F lasks, a lembics, funnels, tubing and other apparatus made of glass were involved in v i r tu - ally all chemical d iscover ies after the 16th century. Beyond optics, glass was essent ia l to physics from the f i rst fr ict ional e lectr ic i ty machines through the Leyden jar , the electroscope, the vacuum pump, to C-eissler and Crookes tubes and their descendants through to today's bubble chamber.

The need for glass having improved optical and chemical propert ies inspired research organizat ions in nineteenth century Germany which foreshadowed the modern industr ia l research laboratory, and re - sulted in Jena glass being used throughout the world in every chemical laboratory and in most optical in- s t ruments at the t ime of World War I. The U.S. gov- e rnment ' s successful glass program during that war in many ways paral le ls the frantic search for subst i - tutes for rubber and other imported mater ia ls in the cr is is of 1942-45.

Glass, of course, is an amorphous, i.e. noncrysta l - l ine, inorganic solid. The elucidation in the ear ly 1930's of its thermodynamic pecul iar i t ies and of its st ructure on the basis of X-ray diffraction was a land- mark in the science of mater ia ls . Many other mate- r ia ls have since been made in amorphous forms, including metals (or rather alloys), and an understanding of the glassy state has merged into the general s t ructura l view of matter upon which all work on mater ia ls must now be based.

Returning to the eighteenth century, the importance of chemical composit ion was part icu lar ly emphasized in studies of ceramics as European potters tr ied desperately to produce more elegant wares comparable with those from China and Japan. Reports by Jesuit miss ionar ies on the manufacture of porcelain st imulated an intensive new examination of minera ls to find colors for glazes and the necessary components of the hard white body (kaolin and petunse, the latter eventually found to be felspar), as well as means of f ir ing ware at temperatures far higher than any previously used in Europe. There followed the f i rst systematic studies of chemical react ions at very high temperatures and the c lassi f icat ion of the var ious kinds of

earth and their interact ions. R~aumur 's "porce la in" (1739) uti l ized the res is tance of divitr i f ied glass to thermal shock and chemical attack. As with metals, the nature of reducing and oxidization atmospheres was exploited. Blowpipe analysis became an important analytical tool after its systematizat ion in Sweden in the 1770's for use on minera ls . This embodied al - most all the old knowledge of fluxes and fusion, oxidation and reduction, v i treous color changes and crysta l - l ization that had accumulated in the pyrotechnical arts and it made an important contribution to further d is - coveries and chemical understanding as well as serv - ing prospectors in the field.

Scientific interest in mineralogy was at f i rst rooted in the knowledge and needs of the miner and the jewel- ler. It took on a different character under the inf lu- ence of the ceramist , from its interact ion with analyt ical chemistry, and especial ly from the attempts at c lassi f icat ion of all natural forms which matured with Linnaeus. Crystal lography acquired the character is t ics of a respectable (i.e. mathematical) science in 1783, when Hafiy saw how to calculate angles between crystal faces in the stacked-box models of c rys - tals that had been suggested ear l ier , and even more so with mathematical space- latt ice theory in the 19th century. However, the physicist in general ignored the internal st ructure of crysta ls because there were few propert ies that could be theoret ical ly derived there- from. The minera logist and prospector meanwhile de- pended on external form and chemical analysis of his minera ls , while chemists used crystal l izat ion for pur i - f ication and identif ication and they were deeply inter - ested in polymorphism and isomorphism, but the quan- t itative success of Dalton's atomic theory (1808) made them assign all propert ies to the f i rst stage of aggre- gation, the simple molecule. For over a century thereafter chemists had to be blind to nonstoichiometr ic solids in order to maintain their belief in the atom!

ORGANIC MATERIALS

The introduction of organic mater ia ls into this story is overdue. Biological mater ia l s appear far less fre- quently in the archaeological record because of their high degradabil ity; they are also less amenab le to scientific study than are s impler inorganic substances. By the selection of parts of var ious plants and animals , mater ia ls can be obtained that have a lmost any combi - nation of desirable propert ies except electrical conductivity or the ability to withstand ext remes of stress and temperature , and man at first had little incentive to exper imenta l synthesis. In the beginnings of scientific organic chemist ry , the needs of med ic ine far outstr ipped other influences. Never the less there is an impor tant stage of its preh is tory recorded in artists' mater ia ls . The color of dyes, lakes and other p igments are dependent upon very subtle aspects of structure, sur face chemist ry , and the effects of pH. The propert ies of po lymer iz ing a lbumen and resins were exploited very ear ly in painter's vehic les and in chinese lacquer, whi le the use of res ins as incense st imulated their d iscovery, but such compounds yielded little to sc ience until the twentieth century A.D.: s imp ler structures had first to be unravel led. Fo l lowing the famous synthesis of u rea in 1828, the synthesis of aniline dyes

614 VOLUME 6A, APRIL 1975 METALLURGICAL TRANSACTIONS A

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Fig. 12--Structural representation of the benzene molecule. F. A. Kekul6, Lehrbuch der Organische Chemic, Vol. II, Erlangen 1862, p. 496.

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from the wastes of the coal-gas industry gave a great impetus to organic chemistry, as well as to la rge-sca le industr ia l research. 9

Structure to the organic chemist meant molecular structure, which only slowly moved from a formula denoting composition, although isomers which had been recognized as being related to the al lotropic forms of e lements like carbon and sulfur known before 1800 A.D., c lear ly involved some internal ster ic factors. 1~ Kekul&s benzene r ing (Fig. 12) was the f i rst step toward the belief that formulae could repre - sent real ar rangements of atoms in space.

THE BEGINNING OF A SYNTHESIS OF VIEWPOINTS

Although the high point of 19th-century mater ia l science was the application of analyt ical chemistry to the discovery of new mater ia ls and the control of old ones, the nucleus of a different type of study was beginning to form--one that would tie everything together and lead to st i l l higher levels of intel lectual, pract ical and social integration. This was the opening of mater ia ls to the methods of the physicist. 11

The successive stages in the development of the science of mater ia ls , and the aspects that at different t imes in the past have seemed most meaningful, can all be seen as related to structure, but to structure on different scales. Repeatedly the excitement at the forefront has come from the identif ication of some previously unsuspected st ructura l feature and the measurement of its interact ion to give a property observed in the larger aggregate. As each unit of s t ruc- tu re , - - "e lement" , atom, phase, chemical molecule, microcrystat , ion, unit cell, electron, nucleus, energy


quantum, vacancies, dislocations and other latt ice im- per fec t ions -was in its turn discovered, it sat is factor i ly accounted for some aspect of matter, but there always remained something unexplained and it was necessary to invent new structura l entit ies both above and below on the ladders of size and energy. Today we are beginning to see that all scales are necessary in wonderful interplay. Although the complex higher levels of st ructure depend upon the propert ies of the smal lest units they are not fully explained by them. Real understanding involves studying the h ierarch ia l whole, but this is beyond our intel lectual capacity and we are forced to tear it to bits for study. Perhaps indeed the very structure of our brain with separate cerebel lum and cerebrum will forever prevent a con- t inuum of understanding between atomist ic and holist ic views.

Among the many discover ies and insights that paved the way to modern solid state physics two were part icular ly important. They were at opposite ends of the structura l ladder, and, unlike the ear l ie r d iscover ies associated with the decorative arts, both were moti - vated by scientif ic curiosity. One started with exper i - ments on a frog's leg, the other with rocks and Shef- field steel. I refer to the discovery of the voltaic e lec- t r ic i ty and to the discovery of the rea l polycrystal l ine microst ructure of mater ia ls by Henry Clifton Sorby. It is ironic that physicists should have discovered electr ic i ty just at the t ime when chemists were aban- doning phlogiston, which was an anticipation of the electron,12 and that the new microst ructure was in some measure a return to the var iable clumping together of corpuscles with which Descartes and his fol lowers had been toying two centur ies ear l ier before a tr iumphant Newtonianism banished such qualitative

VOLUME 6A, APRIL 1975 615

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Fig. 13--Print from electrotype copy of an engraved pIate. Published in the April 1840 issue of Phil. Mag. by Arthur A. Smee, who first used the word "Electrometallurgy" in his Elements of Electrometallurgy, London, 1841.

thinking from respectable science. Each in its own way provided a new access to the

nature of mater ia ls . The microscope made definite many detai ls of s t ructura l heterogeneity that had previously been unappreciated. Measurements of the elec- t r ica l conductivity of var ious mater ia ls at different temperatures revealed a sensit iv i ty to structure on a level quite without precedent~ Of course, fr ict ional e lectr ic i ty was known in ancient t imes, and important exper iments dist inguishing conductors and nonconduc- tors had been done in the eighteenth century. Many effects depending on unrecognized e lectro lys is were known. Fer romagnet i sm had been used in European navigation for over three centur ies (and over five centur ies in China) before it inspired the superb sc ien- tific t reat ise De Magnete of Wil l iam Gilbert in 1600.

The discovery of e lectr ic i ty was an achievement of pure, if empir ical , science, but its development involved a complicated network of interact ions involving people of very different motives and interests each contr ibuting their part. The discovery of magneto- e lectr ic interact ion by Oersted and Faraday preceeded the pract ical motor and generator, and industr ia l use of e lect rochemist ry followed Faraday 's enunciation of the laws of e lectro lys is in 1832. The f i rst steps to these pract ical applications were taken by men without any part icu lar scientif ic t ra in ing or interests . Electroplating, though demonstrated in 1801, lay without pract ical application until 1837, but four years thereafter industr ia l e lectroforming and electroplating were well under way and the production of e lec- trotype pr int ing plates (Fig. 13) had made possible the publication of mass -c i rcu la t ion i l lustrated journals. The copying of coins and plaques was a vast ly popular hobby which introduced innumerable youths, including Werner Von Siemens, to e lectr ica l exper imentat ion and knowledge. The f i rst commerc ia l generator (Fig. 14) was made in 1842 for decorative s i lver plating: today's huge electr ical power industry grew from the desire of the middle class to emulate the gl i tter ing s i lver on the tables of the r ich. 13

Showman Daguerre introduced his famed photo- graphic process at about the same t ime (1839). The daguerreotype, using photoinduced electronic changes in an imperfect s i lver iodide crystal lattice to nucle-


Fig. 14--The earliest commercial generator. Height, 160 cm. Made for use in electroplating by Thomas Prime of Birmingham in 1844. Designed by J. S. Woolrich, who modified an earlier design used in lecture demonstrations of the identity of magneto-electric and voltaic electricity. Courtesy Museum of Science and Industry, Birmingham.

ate local condensation of mercury vapor, wonderfully i l lustrates many pr inciples of so l id-state physics that are now part of what every metal lurg ist should know. Theory however, did not catch up with pract ice for well over a century, and both routes were devious, full of strange turns and meetings.

ON INDUSTRY, MAINLY ELECTRICAL

The electr ic telegraph, coming in the same exciting decade which saw the announcement of photography and plating, provides a fine i l lustrat ion of the way in which the propert ies of mater ia ls can have a great effect upon the course of human affairs. In science, the low voltage electr ic i ty of Galvani and Volta, so easi ly produced and measured, made possible an en- t i re ly new dimension of the study of solids, but such work did not ser ious ly begin until provoked by diffi- culties with the pract ical development of the telegraph. These were inconspicuous compared with the e lectro- magnetic and f inancial uncerta int ies at the t ime, but they are of considerable interest to us.

Fig. 15 is a photograph of a section of the f i rst successful t ransat lant ic telegraph cable. In it are joined not only the actual wires of iron and copper, the f ibers of hemp and the layers of gutta percha, but also many threads of h istory--the iron with its background of powder metal lurgy, welding, of ore reduction in hearth, blastfurnace, and puddling furnace; copper with echoes of man's f i rst delight in metal, soon to excite new studies of alloy constitution based on its var iable conductivity and destined to become the sinews of an un-


Fig. 15--Sections of the first successful transatlantic cables, 1865 and 1866. Both are 2.55 cm diam. See text for details on the materials used.

imaginable new power industry; the hemp rope, reca l l - ing man's f i rst f ibers, weaving (perhaps the f i rst use of a natural mater ia l in a processed form), colonial exploitation, and s lavery; the coal tar used for impreg- nation, at f i rst an undesirable byproduct of gaslighting but then forming the basis of both a new chemical industry and of a new branch of chemical understanding; and last, but by no means least, the insulation provided by an extruded sheath of gutta percha, a natural polymer. The last was an easi ly-molded thermoplast ic introduced from Malaya only a few years previously but it had already been exploited in flexible tubing and as a molding mater ia l in the decorative arts. It was an excellent insulator, and had an advantage over sul fur- hardened rubber in that it was as hard but less br itt le and not corrosive. The overland part of the cable gave new uses for the older mater ia ls glass and porcelain. The technology of shaping the wires of copper and iron had its background in the gold jewelry of the ancient Middle East, in the str ings of musical instruments, in mail a rmor for the warr ior and in t insel for his mis - t ress . It was the culminat ion of a long search for dies and lubr icants and many generat ions of mechanical devices and automatic machines: the wire rod came from a mil l with grooved rol ls f i rst used in the Renaissance for making lead str ips for stained glass windows, or from a sl itt ing mi l l which was the antecedent of all power-dr iven rol l ing machinery.

None of the mater ia ls for the cable was new at the time. Their select ion was based on past experience with them, but the closer scrut iny of their propert ies was to lead, between their t ime and ours, to quite new kinds of thinking in metal lurgy and chemistry, and to a branch of physics embracing all mater ia ls . Every one of these mater ia ls became a source of large prof- its (and losses) in new industr ies having embryo re - search organizat ions and exploiting new process ing methods.

These diverse mater ia ls were brought together not from any scientif ic interest in their propert ies, but because of people's desire to communicate with each other without geographic hindrance on matters of f i - nance, commerce, mi l i tary necessity, polit ics and, not negligibly, love and fr iendship. The pr imary need was a social one, but an idea in the mind of a very few men served to br ing out and br ing together in a new structure things that had been around for some time, and changed them immeasurab ly in doing so.

In emphasiz ing mater ia ls in this d iscussion of the cable I do not mean to min imize the contribution of


physics: the development of practical , sensit ive gal- vanometers and of the theory of conduction, induction and capacity in the c ircuits were as essent ia l to the success of long-distance telegraphy as were the mate- r ia ls , and the~y were new, while the mater ia ls were not. Indeed, well into the twentieth century a user of mate- r ia ls for almost any purpose could specify whatever shapes and sizes he wanted but he had to choose the mater ia l itself f rom a l imited range of more or less standardized composit ions offered by the producers. Research in the mater ia ls industry was done to lower production costs and to standardize the quality of old products rather than to find diverse propert ies optimal ly matched to special ized service needs. A pro- ducer natural ly prefers volume to diversity, and few users were either f inancial ly or intel lectual ly capable of doing much research. Gradually however, some users came to see economy in the use of mater ia ls tai lored to their purposes and after World War I the scientif ic studies of propert ies was encouraged.

Systematic studies of alloys ser ies had been done sporadical ly in the eighteenth century--notably the work on alloys of platinum by H. T. Scheffer and Wil l iam Lewis in the two decades after the importa- tion of signif icant amounts of this metal into Europe in 1750, that by Karl Franz Achard (1788) who studied every physical property then measurable of every possible alloy of all eleven metals than readily avai lable, and the study of alloys for coinage by Charles Hatchett and Henry Cavendish in 1803. The latter was done for the Brit ish government under the aegis of the Royal Society, and seems to be the f i rst systematic study of alloys done with a specific service in mind. (It was concluded that, all things considered, the old composit ions were best.)

In general , in the nineteenth century, most tests of mater ia ls of any kind revolved around the engineers ' need for mater ia ls of more consistent mechanical propert ies and his increasingly scientif ic approach to calculations of the strength of s t ructures. Govern- ment interest was strong, both in regard to public safety 14 and for armament. There was good precedent in the chemical test ing performed by public analysts for assessment of customs duty on l iquors, the control of water supply, and the protection of the public against adulterated products. As far as mechanical propert ies were concerned, proof f i r ings of cannon and guns had long been required by government arsenals . In the mid-nineteenth century extensive laboratory tests of the mater ia ls of which guns and armor were to be made were carr ied out in both Great Britain ~5 and the United States. ~6 At f i rst s imply test ing mater ia ls offered by various commerc ia l sources, the latter program developed into the systematic making and test ing of a ser ies of bronze- l ike alloys by R. H. Thurston re - ported to the U.S. Board for Testing Iron, Steel and other Metals in 1880, and to the f i rst wide-scale use of alloy steel, that of n ickel -steel in battleship armor in 1890. The interest of the Brit ish navy was a strong factor in the organization and support of the fledgling Institute of Metals in 1908. Just a decade later the Institute of Metals Division was formed within the AIME specif ical ly to promote interest in user -or iented metal lurgy.

The manufacturing industr ies were slow to sponsor research on the mater ia ls they used. In the nineteenth

VOLUME 6A, APRIL 1975-617

century the ra i l roads were active in test ing and in writ ing purchase specif ications for standard ferrous and nonferrous alloys and other mater ia ls , but they did not anticipate the advantages that could come from improved special ized alloys. A steel maker started work that gave both s i l i con- i ron for t rans former use and high manganese austenit ic steel. Later, both austenit ic and ferr i t ic stain less steels orginated in s tee l -maker ' s laborator ies, but the greatest impetus came from the automobi le 's need for alloy steels of deeper hardening character ist ics . Except for Henry Ford 's work on low vanadium alloy steels, even the automakers at f i rst only tested what others chose to offer. It was the producers seeking markets for the new alloying e lements- -vanadium, chromium, si l icon, and especial ly nickel--who were most active in studying new alloy steel composit ions, not the steel producers, who reluctant ly made what was demanded.

In the nonferrous metal field, a luminum producers had to catch up with the knowledge of other mater ia ls , especial ly copper, that had been gained empir ica l ly through the ages and they instituted an extensive program of laboratory research. The same pattern was later seen in the new plast ics, which have not yet lost the impetus of their birth in the laboratory.

In general , however, the main st imulus for the d iscovery of new mater ia ls in the last hundred years has come from the electr ical industry. This began with the search for maximizing newly discovered electr ical and magnetic propert ies, but a real change in attitude to mater ia ls developed from the organization of the industry, with research in mater ia ls being required for every new type of device and done in close proximity with specif ication and procurement work. Moreover, insulators and conductors, high and low temperature mater ia ls , ceramics , organics and metals were all involved in close associat ion with each other. All mate- r ia ls came to be seen in competition, with the emphasis only on the propert ies that were needed. There- after every new development in advanced technology-- radar, nuclear reactors , jet a ircraft , computers, and satel l i te communication to name a few--has served to break the ear l ie r close associat ion of mater ia ls re - search with a single type of manufacture, and the modern mater ia ls engineer has emerged.

The viewpoint of the sc ient ist concerned with mate- r ia ls has changed even more than that of his indus- t r ia l counterpart. His interest in a d ivers i ty of propert ies either for basic understanding or in relat ion to service requi rements , and his knowledge of the underlying science which applies to all mater ia ls makes today's mater ia ls scient ist a very different man from the older metal lurg ist who focused mainly on the chemical thermodynamics of production of a single metal. His attitude now is inherently synergist ic , but with its breadth there is an accompanying s impl ic i ty of base. The greatest change from the past l ies, f believe, in the adoption in some measure of the physic ist 's view of the world without loss of an interest in pract ical diversity.

Both the science and the practice of e lectr ic i ty after the middle of the nineteenth century helped to shape a watershed in the history of mater ia ls , as in much else. In addition to its f i rst commerc ia l uses in e lectroplat- ing and electroforming, industr ia l e lect rochemist ry

Fig. 16--Portion of a copper cathode made in the refinery of Elkington, Mason and Co. before 1880. In 1878 James Elking- ton reported to John Percy that the production of electrolytic copper had averaged six tons per week for the previous nine years. Specimen 901, Percy Collection; Courtesy of Science Museum, London.

quickly gave high purity copper (Fig. 16) which in its turn became essent ia l to the power industry, and, a l itt le later, cheap aluminum, ferroal loys, chlorine, graphite, abrasives, and much else. The effect on the science of mater ia ls was even more profound, for it allowed the measurement of new propert ies and re - vealed the different c lasses of behavior in metal l ic and ionic conductors, dialectics, and semiconductors. Up to the nineteenth century v i r tual ly no uses of mater ia ls had exploited anything beyond their mechanical or optical qualit ies or their res is tance to corrosion. The only physical propert ies to be widely measured and reported quantitatively in scientif ic l i terature were melt ing point, density, thermal expansivity, and specific heat. Mechanical propert ies (except elastic constants) seemed to be too var iable to have much basic signif icance.

The f i rst systematic studies of the conductivity of alloys were done to meet the pract ical needs of Atlan- tic cable. The f i rst conductors had been purchased without any specif ication of conductivity, and one length of cable using arsenica l copper from Rio Tinto was found to have 14 pct of the expected conductivity! Only 400 miles of the 2500-mile cable laid in 1857 were tested, and Kelvin said that the speed of t ransmiss ion of messages would have been 30 pct greater had specif ications been used throughout. Thereafter Mathiessen in 1859-63 measured the conductivity in many different alloy systems, and tr ied to relate their quite different behaviors to solid solution or immisc ib i l i ty or compound formation in a thoroughly modern way. The re - s istance thermometer was also an outgrowth of the cable studies. For a few years thermoelectr ic i ty was a leading tool in alloy studies. It drew attention to the cr i t ical point in steel, and above all, it later gave an ideal pyrometer for meta l lurg is ts ' use in plant and laboratory. It was actually used for measur ing temperatures of b last - furnace air in 1865, two decades before its use in alloy constitution studies in the laboratory! E lectr ica l measurements on mater ia ls were part icu lar ly important to theoret ical physics. The recognit ion of the near ly exact relat ion between ther - mal and e lectr ica l conductivit ies (Wiedemann-Franz,

618 VOLUME 6A,APRIL 1975 METALLURGICAL TRANSACTIONSA

84149

Fig. 17 - -Carbon F i lament lamp, Ed ison "A" type, 1879. This lamp uses a f i lament of carbon ized bristol board, and was purged by outgassing before sealing. Note the platinum clamps holding the ends o[ the carbon filament, the platinum/lead- glass seal, and the exterior lead wires of copper wound telegraph-fashion around the platinum. Courtesy of Greenfield Village and Henry Ford Museum, Dearborn, Michigan.

1853) led, after the discovery of the electron, to fer - ti le e lectron-gas theor ies of the metal l ic state, r ipe for the introduction of quantum theory later.

New mater ia ls for the incandescent electr ic lamp gave a part icular l ivel iness to mater ia ls research, but it must be noted that neither the carbon f i laments of 1880 (Fig. 17) nor the ductile tungsten f i laments of 1910 were developed by professional mater ia ls men. Work on tungsten served metal lurgy well by causing a rena issance of powder metal lurgy and focussing theoret ical attention on grain shape and on grain growth mechanisms, while Edison's work on carbon- ization was an ancestor of today's extremely strong carbon f ibers.

Physicists, metal lurg ists and ceramic is ts have col- laborated part icu lar ly effectively in dealing with magnetic mater ia ls . The abrupt change of magnetization of i ron with temperature had been noted by Gilbert in 1600; magnetic changes in brass , later associated with precipitat ion of i ron and the breaking of latt ice coher- ence by deformation, were studied in the 1750's. In the late nineteenth century, var ious cobalt and tungsten steels were found to yield super ior permanent magnets. Equally important was the observat ion of soft magnetic mater ia ls - -espec ia l ly the discovery in 1899 of low-hys- teres is si l icon iron by an Ir ish physicist Wil l iam Bar- rett measur ing metal lurg ist Hadfield's samples. The development of magnetic domain theory meshed easi ly with meta l lurg is ts ' s t ructura l thinking. Work by met- a l lurgists on the orientation relat ionships during pre - cipitation laid the ground for or iented-part ic le magnets, and metal lurgical knowledge of the ways in which the topology and energy of grain boundaries affected their motion was behind both improved t rans former iron and soft ferr i tes . However, the development of semiconductors in the 1940's and 50's needed an acquaintance with structure in a different kind of space, and meta l lurg is ts ' ideas were not as useful as were their fabrication techniques, which were essential .

The leaders in the study of e lectr ical propert ies were all physic ists. It is t ime to return to the field which is the pr incipal contribution of metal lurgy to modern science, namely metallography, the core of which is the relat ion of microst ructure to composit ion and propert ies. 1~

METALLOGRAPHY

The study of the microst ructure of metals began with Sorby in Sheffield in 1863-64 but it did not develop ser ious ly until the eighties. As in all areas of science, contributions came from many countr ies. Curiously, not one of the imaginative men who started metal lography in England, Russia, Germany, France and the United States (Sorby, Tschernoff, Martens, Osmond and Saveur) was working in an academic en- v i ronment, and only in France, where Osmond soon moved to the University of Par is , was the pioneer work followed immediately by steady development involving other sc ient ists. 17

The ear l ie r alloy studies had mainly served simply to consolidate the chemical approach. Segregation in ingots for coinage was the reason for the f i rst deter - mination of an alloy constitution diagram at temperatures inaccessible to the mercury thermometer - - the s i lver -copper diagram establ ished in 1874 by Roberts- Austen using a quenching ca lor imeter to measure temperatures. In 1887 Flor is Osmond beautiful ly combined the two new techniques of microscopic metal lography and thermal analysis in his studies of the hardening mechanism of steel. His results were ref ined into a good i ron-carbon constitution diagram by Roberts- Austen, and corrected to accord with the phase rule by the Dutch physical chemist Roozeboom in 1898.

For the f i rst two decades of the twentieth century all advanced metal lurgical work was done by people who, though they began proudly to call themselves metal lographers, had been tra ined as chemists, and much of it involved the determinat ion of constitution diagrams of more and more alloy systems. It was


natural for them to observe the phases present in the microstructure, for this was a simple extension of the macroscopic phase separation upon which all chemistry was based. They also studied other features of microcrystalline shape and texture and related them to industrial treatment, to mechanical properties and to service failures. It was a time of exploration, mapping a large world of essentially unknown territory. It confirmed the polycrystalline nature of all metals and replaced the old fracture tests with a more realistic measure of structure. The complexity of the behavior of steel as well as its economic importance invited more attention to it then to any other alloys, with results permanently preserved in the terms used by metallographers for their structures and for the types of transformation that give rise to them. By 1910, most undesirable qualities in metals, which in the analytical period of metallurgical advance had been explained simply in terms of the presence of impurities, had been more usefully explained as due to the inter- granular distribution of minor phases, which could now often be changed because it could be seen.

By the 1930's the optical microscope had revealed most of the features that are open to its scale of reso- lution, microns to millimeters. It had taken the important place in the control of industrial production and in the investigation of failures that it still holds. In the early fifties, metallography became quantitative following the application of statistical geometry to two- dimensional sections, and the elucidation of the role of interface energy equilibrium provided a unified explanation for the diversity of structures that had been cata- logued. In the last fifty years however, the most active research has been related to structure at levels inaccessible to the optical microscope.

Many changes in metallurgy in the last century have come from the discovery and practical application of nontraditional properties. Nevertheless, the old mechanical properties were far from forgotten. At first there were only marginal improvements based on alloying and grain size control, but a new territory was opened with precipitation hardening. This was an em- pirical discovery, completely without theoretical anticipation or without any earlier uses in the arts (un- less Chinese celadon and red glazes, opal glass, magnetic brass, temper brittleness or some hard dental alloys can be so regarded). It is the only method of hardening metals that was not known in prec lass ica l t imes. Although ster l ing s i lver is readi ly hardened simply by slowly cooling after annealing, I have not found a single reference to a s i l versmi th 's having no- ticed this, or even the fact that the metal is more mal - leable if it has been quenched. The discovery of precipitation hardening, or age hardening as it was f i rst called, was made in 1906 by a German metal lurgist , Adolf Wilm, in the course of a methodical study of a luminum alloys. This was announced in 1911 just in t ime to provide light a luminum alloys for the burgeon- ing a i rcraf t industry. At f i rst a mystery, it soon turned metal lurgical thinking to a new level of st ructure below that of their beloved microscope. A reasonably correct explanation was provided within a decade by the great American metal lurg ist Paul Merica, and this s t imulated the discovery of many alloys of other metals that were capable of hardening by the same mechanism, as well as hardening by second-phase d ispers ion produced


by means other than temperature-dependent changes of solubil ity.

Far greater changes were in store for mater ia ls as a direct consequence of changes in the nature of physics occurr ing at about the same time.

X-RAY DIFFRACTION

In the nineteenth century, physicists' attempts to provide a theoretical understanding of solids had been limited mainly to studies of the elastic anistropy of crystals. In 1900 came the electron-gas theory of metals which gave fair results for the relation between thermal and electrical conductivities, but failed on specific heats. Planck's quantum theory, and the develop- ments of it by Born, Debye, Schr6dinger, Slater and others between 1912 and 1926 were of immense importance in establishing the theoretical basis of solid- state physics, but it was some decades before it led to ideas that the more practical materials man could use. Quite a different reception was accorded the discovery of X-ray diffraction, which provided for the first time in history an experimental measure of structure fundamental enough to appeal to the physicist and at the same time directly relatable to the diversity of material types known to the practical user. The first development of the field was quite different in different countries, again demonstrating the inter- active nature of nucleus-development in science.

Von Laue and his collaborators performed their famed demonstration of diffraction with copper sulfate in 1912. This was in Munich, and one might have expected immediate explosive interaction with the work going on in the world's leading center of chemical crystallography under the direction of P. Groth in the same city. Nothing of the kind occurred, and for sev- eral years the main interest in Germany remained in the mathematical aspects of the diffraction phenomenon itself and what it could tell about the nature of radiation-the essence of traditional physics. A quite different view was developed in England with the work of the W. H. Bragg and especially that of his son W. L. Bragg, who, using elegant but simple theory, turned the effect into the most important tool for the study of solids ever developed. TM The structure of crystals quickly became an ideal subject for scientific research combining as it did opportunity for ingenious experimenta- tion and mathematical analysis at both rudimentary and highly sophisticated levels, together with clearly envisaged areas of practical utility.

Crystal chemists and mineralogists at last had real data on the effective sizes of atoms in different states of ionization, and symmetry came to reside inside the unit cell. Combining crystallography with new quantum theory, the different classes of solid which the six- teenth-century iatrochemist Paracelsus has sensed as related to this three principles of salt, sulfur, and mercury became examples of types of interatomic binding, ionic, van de Waal's and metallic. (Regretably, Para- celsus overlooked covalent-bonded diamond!) Even the most practical metallurgist, already sensitized to the importance of structure in general, could appreciate the models of cubic and hexagonal lattices that were shown to him. By 1930 X-ray diffraction equipment was common in metallurgical laboratories throughout the world, and advanced metallurgical thinking was

METALLURGICAL TRANSACTIONSA

mainly concerned with st ructure on the atomic level. The molecule, that clumping of a few Daltonian atoms which had dominated thinking to the point where it had become the basis of almost all explanations of proper- t ies of mater ia ls in the nineteenth century, disappeared from consideration of inorganic solids. It was two decades before diffraction techniques advanced to the point where they could deal effectively with the molecular crysta ls of organic chemistry, but eventually even complicated biological ly important molecules became real s t ructura l ar rangements in space--and the hypothecated genetic code became the real structure of a molecule. The development of ideas on the structure of synthetic polymers eventually came to bridge the gap between the n ineteenth-century chemist 's molecule and the ear ly - twent ieth-century crystal , so paving the way for the unified structura l view of all mater ia ls which we see taking shape today.

The real izat ion of the role of crystal imperfect ions was the next important phase. This began with ionic crysta ls . Somewhat implausible "mosa ic" st ructures were advanced to account for d iscrepancies between theoret ical and exper imental intensit ies of diffracted X-rays, but the f i rst real success came from explanations of the effect of radiation and departures from stoichiometry on the color and conductivity of alkal i - halide crysta ls whose st ructures were now well known: electronic excitons and vacancies and/or interst i t ia l ions in the lattice could be formed and then moved ran- domly by thermal excitation or direct ional ly by gradi - ents in e lectr ical field or composit ion to give ionic conduction or chemical diffusion. Next the var iable de- gree of order and disorder in crystal latt ices of certain alloys was elucidated exper imental ly and formal ly re - lated to other cooperative phenomenon such as the fer - romagnetic Curie point. The last form of imperfect ion to be accepted, in many ways the simplest, was the lattice dislocation which plays the essent ia l role in the plast ic ity of crysta l l ine mater ia ls .

None of these imperfect ions could have been thought of until the crystal lattice itself had become a real i ty in thinking about matter , but once this had become common they are all easi ly v isual ized as simple local geometric configurations pers ist ing in a sea of order to which they do not conform. They are the inverse of the ordered cluster of Dalton's molecules in a random liquid. Lattice imperfect ions and comparable positive and negative holes in electronic energy levels in semi - conductors are the very essence of h ierarchica l s t ructure. They cannot exist at a single level, but are formed by an interact ion between a local condition and an extended ordered environment. Philosophically they marked a turn away from the age-old concern of the physical sc ient ist with idealized atomist ic order or fully randomized disorder and they forced him to take a step toward the complexity of real mater ia ls .

This view was reinforced by the next exper imental advance, the introduction of the electron microscope in three successive forms- - rep l ica , t ransmiss ion and scanning. These inst ruments revealed the complex nature of the patterns of interact ion between the im- perfections themselves, and they have had somewhat the same effect in convincing sceptics of the importance of structure and of opening an ent irely new world to exper imental study that the optical microscope had

had in metal lurgy three quarters of a century ear l ier and in biology long before that.

CHANGES IN PROFESSIONAL OUTLOOK

As we have seen, the activit ies of the men pract ic - ing metal lurgy were continually modified by input from the pure sciences, usually in the form of better understanding of empir ica l ly known behavior. But the development of a useful chemistry of mater ia ls in the 19th century changed the attitude of chemists as well as their opportunit ies of employment. The same thing seems to be happening in physics following the development of a useful solid state physics.

The new mode of thinking was especial ly evident in the electronic industry that burgeoned after World War II. None of the new possibi l i t ies of sol id-state e lectron- ics could be real ized without the production of mate- r ia ls on a commerc ia l scale to standards of chemical purity and crystal lographic perfection and imperfec- tion that would have been inconceivably high only a decade before. Though metal lurgists played an essential part in the ear ly development of pract ical semi - conductor devices, most people engaged in such work today like to regard themselves as physicists. Once confined to an academic elite, the Amer ican Physical Society now includes a substantial fract ion of members who are industr ia l ly employed, and more Ph.D. 's are concerned with solid state physics than with any other branch. 19 Nevertheless, a deep understanding of solid state physics is an essent ia l part of the equipment of mater ia ls engineers, for many of them more important than a knowledge of mining and smelt ing with which his profession began. A reshuff l ing of organizat ions to re - f lect the new pr ior i t ies would seem to be in order, both to allow for status- inf lat ion of professional terminology of people doing useful work as well as to free a few individuals from the social pressure toward relevance that res t r i c ts untrammeled thought.

Changes quite as great as those in science have occurred in the engineer ing aspects of our profession. The future will certainly see increased emphasis upon extraction and process ing in response to the exhaustion of high grade ores and the necess i ty for conservation of whatever already has been extracted. Indeed there is probably, at the moment, more room for imaginative scientif ic research on processing mater ia ls than on their end uses. Moreover, the two are simply parts of a cycle--there is no end use. Scrap has always been reused to some extent, and the new ecology of mater i - als will necessitate more awareness of the whole balance by the pract i t ioners of any one part. The ingenuity that in the past went to extracting metals from ever more difficult ores will work on what is now called refuse, and the "user" of mater ia ls , will have to real ize that though he may be at the apex, he, like an animal in the carbon cycle in nature, is concerned with

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