UNCLASSIFIEDJL

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ARMED SERVICES TECHNICAL INFORMION AGENCYARLINGTON HALL STATRNA-ROM,1~ 12o V10IRIAj

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i UNCLASSIFIED

NOTICE: Mhen government or other drawings, speci-fications or other data are used for any purposeother than in connection vith a definitely relatedgovernment procurement operation, the U. S.Government thereby incurs no responsibility, nor anyobligation vbatsoeverj and the fact that the Govern-ment may have formuated, furnished) or in any waysupplied the said drawings) specificationsp or otherdata is not to be regarded by implication or other-wisa as in any manner licensing the holder or anyother person or corportion, or conveying any rightsor peznission to manufacture, use or sell anypatented invention that my in any way be relatedthereto.

A$D-T0R412U4

COMPARISON OF HIGH ENERGY RATE(DYNAPAK) AND CONVENTIONAL

EXTRUSION OF REFRACTORY METALS

'Mmw TECHNICAL DOCUMENTARY REPORT NR ASD-TDR-62-506September 1962

Directorate of Materials and Processes... Aeronautical Systems Division

Air Force System Command

Wtlght-Patteron Air Fore Base, Ohio

Project No. 7381, Task No. 73811

(Prepared under Contract Nr AF 33(616)-7842 by theWestinghouse Electric Corporation, Blairsville, Pennsylvania;

Dirk 0. Rabenold, author.)

I

This report was prepared by the 1aterels Munufaoturing Division ofWestinghouse Eleotric Corporation under USA Contract No. AF 33(616)-7842. Thiscontract vas initiated under Project No. 7381s, Tat No. 73861.. The work wsat.nistered tauder the direction of the Directorate Of 1aterials and PromesesDeputy Oinander/eeohnoloap Aeronauti,•a Sytem Divisions with U., 0. .X.Pierce acting as projfect enosears.

This report covers work conducted from March 1961 to March 1962.

hits work was conducted at the Materials 1Manufacturing Division of Weetinioue,Blair"vflles Peonsylvan•a, and at the Amsrican Brake Shoo Compay• Researchlaboratories, Mahwah, Now Jersey* Siliifcant contributions were Cds to tUeproject by Mr. D. H. Moreno of Westingbouse, and by technical personnel of theAmerican Brake Shoe canpaqn.

AB82R9M

A ocIarson was made of the surface quality, dimensions, ohemsdtry, hrdess,tensrle properties, and reorystellization behavior or extrusions produced on aModel 1810 Dymapak high-velocity mohine and on a 700-ton Loemy high speed. ox-trusion press. Shree temperatures wore established which represented hot work,cold work, acd a combination of hot and cold work, by making preliminary extrusionson the Dynapak mchine. Are cast billets, with a nomiml diseute of three Inches#of two refractory alloys, a Mo-25d-O.lZr alloy .&d a 'J-0.60b alloy, were then ex-truded at a constant 4:1 reduction ratio from the same three temperatures on bothmaohines. She results of this work indicate that equally good surfaces can beobtained from either process when proper ldbricatIon an die preparation teohniquesare used; a lower hot working temperature can be used for hIgh-velocity extrusions;and, a lower recrystallization temperature Is obtained In material cold worked onthe Dymapk. fte latter fact Indicates that high-velooity-extruded metals retaina higher de•gree of internal stress than conventionally-extruded metals.

WTs taechnol . doomm.tu report hs bmeu revime and Is approved*

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PI"_.S SoI0QUU ON "mW

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TANM OF CONTSIMS

PAGE

II. EXIUDU AL, PROcE1tOeneral 2Billet Preparation 2Machine and Tools 3Beating ProaeLures 4Extrusion Prameters 5Sampling and Evaluating Techniques 5

PASE I OLUBNMU ALLOY EX•USIONS

MI. RXUI4LTBase Informwtion Extrusions 6Pftrsm Ext~rusi:lons

Surface Evaluation 7Dimiensions 7Chemistry 9sufness 9Tensile Properties 9Morostruoture 10Rearystaeli.ation Behavior 11.

IV. DISCUSIO 11

PHASE 11 •i•OSTIN ALLOUM E••USION

V. MESULTBBase Informtion Extrusions 12Program Extrusions

Surface EvaluationDiimens ionsNChemistry 15Hardness 15Tensile Properties 15

:icrostruoture 15Recrystallization Behavior 16

VI. DISCUSSION 17

VII. MEURAL COWLUSIONS 18

VIII. ECOMIWIDATIONS 18

1K. REPIENCES 19iT

LIST OF FIGURES

FIGURE PAGE

1. Sketch Showin the Position of Billets, Macro Slices, and 20Chemical Analysis Samples in the Original Ingot

2. Examples of Longitudinal and Transverse Macrostructure and 21Longitudinal Miorostructure (IOOX) of As-Cast MolybdenumAlloy Ingots

3. Example of Transverse Macrostructure and Longitudinal Micro- 22structure (10OX) of As-Cast TUngsten Alloy Ingots

4. General View of 70T-Ton Loewy High Speed Extrusion Press 23Showing Proximity of Billet Heating Furnace

5. General View of Model 1810 Dynapak Machine Showing Proximity 24of Billet Heating Furnace

6. Sampling Technique Used for the High Speed Press and Dynapak 25

Extrusions

7. Base Infomation Dynapak Extrusionm In the As-Extruded Condition 26

8. huse Informtion Dylpak ExtrusLon@ in the As-Extruded Condition 27

9. Longitudinal Micrographs (1OOX) and Extruding Temperatures of 28Base Inforumtion Dynapek Extruded Molybdenum Alloy Bars

10. High Speed Press Extruded Bars. As Extruded from 2700OF 29

U1. High Speed Press Extruded Bars. As Extruded from 29500F 30

12. High Speed Press Extruded Bars. .As Extruded from 3%W000 31

13. Dynapak Extruded Bars. As Extruded from 2700OF 32

14. Dynapak Extruded Beaus. As Extruded from 2950oF 33

15. Dympak Extruded Bars. As Extruded from 35000F 34

16. Extrusion aonstant (K) vs Temperature for the Dynapak and High 35Speed Press Extrusions of the Mo-25W-O.lZr Alloy

17. High Speed Press Extrusion Dies After One Extrusion of the Billets 36Indicated

LIST OF FIGURES (continued)

18. Hzigt Temperature Tensile Strength vs Hardness for the Dynapak 37and. High Speed Press Extruded. Mo-25W-O.lZr Alloy

19. Longitudnial Micrographs (100X) and Extruding Temperatures 38of High Speed Press Extruded Molybdenum Alloy Bars

20. Longitudinal Micrographs of High Speed Press Extruded 39Molybdenum Alloy Bars

21. Longitudinal Miorographs (1OX) and Extruding Temperatures 40of Dynapak Extruded Molybdenum Alloy Bars

22. Longitudinal Micrographs (1OOX) of Dyxapak Extruded Molybdenum 41Alloy Bars

23. Longitudinal Micrographs (OOX) and Extruding Temperaturesof Hih Speed Press Extruded Molybdenum Alloy Bars BeatTreated for one Hour at 2900°F

214. Longitudinal Micrographs (loox) and. Extruding Temperatures 143of DVnapak Extruded Molybdenum Alloy Bars Heat Treated forOne Hour at 2900OF

25. Hardness vs Raorystallization Annealing Temperature for the 44Dyapak and High Speed Press Extruded No-25W-0O.Zr Alloy

26. Base Information Dynapsk Extruded Tungsten Alloy BEars. As 4Extruded from the Adicated Temperatures

27. Base Informatiot Dynapak Extruded Tungsten Alloy Bars. As 16Extruded from the Indicated Temperatures

28. Longitudinal Micrographs (100X) and Extruding Temperatures of 47Base Information Dymapek Extruded Tungsten Alloy Brs

29. High Speed Press Extruded. Tungsten Alloy Bars. As Extruded.:1from 2800oF

30. High Speed Press Extruded Tungsten Alloy Bars. As Extruded 49from 3100OF

31. High Speed Press Extruded Tungsten Alloy krs. As Extruded 50from 3400OF

32. Dynapak Extruded Tungsten Alloy Bars. As Extruded from 2800OF 51

33. Dyapak Extruded Tungsten Alloy Bars. As Extruded from 3100OF 52

vi

LIST OF FIGURES (continued)

FIGURE PAUK

34. Dynapak Extruded Tungsten Alloy Bars. As Extruded from 3400OF 5335- Extrusion Constant (K) ve Temperature for the Dynpapk sand 54Hg Spee Press Extrusion of the Tungsten - 0.60b Alloy

36. High Speed Press Extrusion Dies After One Extrusion of the 55Tungsten Alloy Billets Wioated

37. Dyapak Extrusion Dies After One Extrusion of the Tungsten 56Alloy Billets -adicated

38. High Temperature Tensile Strength vs Hardness for the Dynapak 57and High Speed Press Extruded Tungsten - O.6cb Alloy

39, Longitudinal Micrographs (10OX) and Extruding Temperatures 58of High Speed Press Extruded Tungsten Alloy Bars

40. Longitudinal Miorographs of High Speed Press Extruded Tungsten 59Alloy Bars

41. Lwgitudinal. Mirographs (1ox) an Extr'iing Tepratures 60

of DWymaak Axtro)ed .U t•xen Alloy Bars

42. Lngitudinal Xiorographi (OOX) of Dynapsk Extrudede Tungsten 61Alloy Bare

413. Lomgitudi1nal lMiorographs (10x) end. Extruding TemPeratures of 62High Speed Press Extruded Tungsten Alloy. Bars Heat Treatedtor One Hour

44. Longitudinal microgaphs (iOox) ad Extruding Temperatures of 63Dynpak Extruded Tungsten Alloy. Bars Beat Treated for One Hour

15. Hardness vs Reorystall.ation Annealing Temperature for the 614Dymnpak and High Speed Press Extruded Tungsten - O.60b Alloy

LIST OF TABLIS

[TOME zgt PAGEh1 Dimensions, Chemistry and Hardness of Arc Cast Mo-25W-O.lZr 65Alloy Ingots

2 Dimensions, Chemistry and Hardness of Arc Cast W-0.6cb Alloy 67Ingots

3 Extrusion Parameters Used for Dynapek Extruding the Mo-25W-O.lZr 69Alloy

4 Extrusion Parameters Used for High Speed Press Extruding the 70Mo-25W-o.lZr Alloy: Extrusion Parameters Used for Dynapak Extruding the W-O.60b Alloy 71

6 Extrusion Parameters Used for High Speed Press Extruding the 72w-o.6cb Alloy

7 Dimensions, Volumes, K Values and Energy Values for Dynapak 73Extruded Molybdenum Alloy Bars

8 Dimensions, Forces and K Values for High Speed Press Extruded 75Molybdenum Alloy Bars

9 Extrusion Die Bore Diameter Before and After Extruding the 76Molybdenum Alloy Bars

10 Chemistry and Hardess of Dynapak Extruded Molybdenum Alloy Bars 77

11 Chemistry and Hardness of Hi&h Speed Press Extruded Molybdenum 78Alloy Bars

12 Tensile Properties of Dynapak Extruded Molybdenum Alloy Bars 79

13 Tensile Properties of High Speed Press Extruded Molybdenum Alloy 80Bars

14 Dimensions, Volumes,K Values and Energy Values fbr Dynapak 81Extruded. Tungsten Alloy Bares

15 Dimensions, Forces and K Values for High Speed Press Extruded 83Tungsten Alloy Bars

16 Extrusion Die Bore Diameter Before and After Extruding the Tungsten 84Alloy Bars

TiU1

LIST OF TABLES (Continued)

*TABEI PAGE

3.7 Chemistry and Hardness of Dynapak Extruded Tungsten Alloy Bars 85

18 Chemistry and Hardness of High Speed Press Extruded Tungsten 86Alloy hisr

19 Tensi1e Properties of Dynapak Extruded Tungsten Alloy Bars 87

20 Tensile Properties of High Speed Press Extruded Tungsten Alloy 88Bars

21 Approximate Amounts of Recrysta•llization and Average Grain Size 89in the As Extruded Condition fOr High Speed Press and DynapakExtruded Tungsten Alloy Bars

DnM0DWTION

The state-of-the-art of extruding metals ban advanced in recent years to thepoint where high strength molybdenum alloys can be successfully extruded into roundbas and shapes. Very recently, tungsten alloys also have been extruded with somesuccess. The introduction of high energy rate machines in the past few years hasmade available a new tool for both forgIng and extrusion work. Because of theextremely rapid working accomplished by these machines, it appeared that severaladvantages could be obtained by using them for extruding refractory metals.

1. The short working time would prevent excessive die wear by decreasingthe contact time between refractory metals and the tooling at hightemperature.,

2. Higher temperatures would be allowed because of this short contact time.

3. The combination of rapid working and allowable high temperatures wouldproduce more favorable conditions for converting the coarse dendriticstructure of arc-cast billets to a completely recrystallized structure.

2W purpose of this contract was to compare the quality, dimensions, metall-urgiaal characteristicsm, and physical properties of highly refractory materialswhen extruded by the high energy rate (Dynapak) and the conventional extrusionprocess. SU cmarison would then allow a e knovleeable decision regardingwhich process would effect the best combination of material characteristics for apartWular applicatin. Fr thi co• ison, three-inch diameter arc-cast billets(bilts for the hiOh-velocity process were actually machined to a dianeter of2-7/8 Inches) of a Mo-.5W-0.1Zr alloy and a W-O.60b alloy were chosen to be extrudedby the two processes from three temperatures. *hese two alloys were chosen becausefor these alloys there presently exists conventional extrusion experience and hightemperature tensile tent data which would assist in the comparison. ft threetemperatures were to produce, respectively, 100$ hot work, 100% cold work, and

'approximately equal amounts of hot and cold work. Furthermore, the three temper-atures were to be established by examining high-velooity extrusions and then thesam three temperatures used for each process.

At the beginning of this contract, it was planned to meke the high-velocityextrusions on a Model 1210 Dymapak machine. It soon became apparent, however, thatthe 150,000 ft. lbs. of energy of the machine could not extrude a sufficient volumeof a three-inch diameter billet to be evaluated. As a result, negotiations wereconcluded with the American Brake Shoe Company to use their larger Model 1810Dyapak machine vhich delivers an impact energy of 430,000 ft. lbs.

A unique feature of this investigation was the fact that a constant fairlysmall reduction ratio of 14:1 was maintained for all the extrusions regardless of

Manuscript released by author June 1962 for publication as an ASD TechnicalDocumentary Report

the process or the teeture used. This Permitted. be W er evaluation of the

effect of temeratures end extrusion rates on the rec:,,xt'tstion behavior ofthe as-east structure and the uniformity of work in ihý metruaea structure.

1. EXGeneraTAL PRO•EI

fhe general procedure laid out for this contract was to extrude by hgh-velocity methods a sufficient number of billets to establish three temeraturesthat would produce 100% hot vork, 100% cold work, and an Intermediate structure.Tvo as-east billets would then be extruded at each of these temperatures on eachof two machines: a Dynapak machine and a conventional extrusion press.

MlYbdenum. Allay

A total of nineteen extrusion. were made for this phase of the contract.Seven base-information extruslons were made by high-velocity techniques, one ofwhich was subsequently used for a progpam extrusion. Five progam extrusions weremade on the Dynspak and seven pro . extrusions vere made on a conventional ex-trusion press. One of the latter was made =rely to establish the operatingcharacteristics of the extrusion press and Instrummnts.

A total of nineteen extrusions wer eode for this pNase of the contract.Six billets were used for the base-inormation work on the hi&-velocity mahine.So base-informtIon press extrusians were rode, but the ,nfop•mtio, from the mlyb-denum press extrusions was used to assist in this work. Six Dynpapk extrusionsend seven press extrusions wer then made for the com•s•lion. the extra pressextrusion va made to replace one which required a long transfer time from furnaceto press.

2. Billet Preparation

MLl• mnm A3llw

1ihe billets for this peart of the contract were Obtained from eiht vacuum-&rc-cast Inipts melted at the Westinghouse M1terl&s Manufacturing Division, BMainville,Pennsylvania. uhe eleotrod material was purchased f•o t General Electric Can-pan as preblended and sintered bar measuring approxima ely two inches in diameterby 29 to 27 Inches In length. Bach bar had a 1/8-inch diameter cored hole In thecenter extending the full length of the bar. Bach end of each bar was drilled andtapped to provide a female thread 3/4 Inaehes x 30 x 1-1/8 Inches deep. ee barsvere then Joined by a 'tud to form a finished electrode 80 to 84 Inches long.

Zirconium was aded by Inserting the proper amount of 0.076-inch diameterzironium wire through the cored hole and extending 3/8 Inches beyond ae end.the electrodes were melte into 3-1/2-inch diameter copper molds with approxiamtely

2

3500 amperes and 28 volts. Malting time was 21 minutes for an ingot 22 incheslong.

After the hot top and bottom sections of each ingot were removed, a 1/8-inch slice was out from the top and bottom ends and sampled for chemical analysis.Ecu ingot was then machined to 3.00 inches in diameter and ultrasonically tested.Further sectioning of the Ingots is indicated in Figure 1. In some cases, fourthree-Inch lengths were obtained. Those ingots used to provide high-velocity ex-trusion billets were further machined to 2.875 inches in diameter. Mhe 5-1/2 inchlength shown In the sketch was used for a different program. A 1200 chamfer wasmachined on each billet 1/4 inch back from the top end. Hardness readings weretaken on the top and bottom ends of each billet. Finally, a glass lubricant wassprayed onto the surface of the material to a depth of 0.010 to 0.015 inch.

The dimensions, chemistry, nd hardness of the as-cast ingots are presentedin Table 1. Chemical analyses were made at the Materials Manufacturing Division.An Indication of the homogeneity of the as-cast ingots can be seen in Figure 2which shows four typical transverse macrogaphs and one longitudinal section. Italso shows the typical microstructure of the as-cast material.

Tuagsten Alloy

Me billets for this portion of the contract were purchased from the Refracto-met Division of the Universal Cyclops Steel Corporation. Each Ingot was machinedat Universal Cyclops to 3.00 Inches in diaueter and was ultrasonically tested.

A 1200 choafer, 1/i-iSnh back from the top end, was also machined on eachbillet at Universal Cyclops. Hardness readings were taken on the top and thebottom end at the edge eard mid-radius positions. Finally, a glass lubricant wassprayed onto the surface of the material to a depth of 0.010 to 0.015 inch on theradius.

The dimensions, chemistry# and hardness of the as-cast ingots are presentedin Table 2. The analyses shown are those reported by Universal Cyclops. Thehomogneity of the as-cast ingot structure can be seen in Figure 3 which showstypical longitudial microstructure (1OOX) and transverse macrostructure (lx) ofthe as-cast tungsten-columbium alloy Ingot.

3. Machines and Tools

The same equipment was used for both the molybdenum alloy extrusions and thetungsten alloy extrusions. The two machines used for this work (Figures 4 and 5)were a 700-ton Loewy high speed press and a Model 1810 Dynapak machine anufacturedby the Convair Division of the General Dynamics Corporation. The Loewy press candeliver an effective constant force of 600 tons at a speed of 14 inches per second,which is higher than other conventional presses. In contrast the Model 1810 Dynapakmachine delivers a maximum impact energ of 430,000 foot-pounds at an Initial speedof approximately 900 inches per second. No special tooling was used on the conven-tional press and the tooling usedljj the high-velocity machine was similar In de-sign to that described by Reimann '. The diameter of the container on the presswas 3-1/8 inches and that used for the high-velocity machine was 3 inches.

3

All dies were made from 113 tool steel and were provided with a 1200 entrance angle.The dies for both the high-velocity and conventional extrusions of the tungstenalloy were coated with a 0.020- to O.05-inch thick layer of zirconia by the plasmaflame spray technique. The coating vas underlayed with a 0.003- to 0.005-inchthick layer of a nickel-chromium alloy. Uncoated dies were used for all the molyb-denum extrusions.

•. •ettg Prcedu..-es

All billets were heated in specially constructed induction heating furnaces.The furnace used at the Anerican Brake Shoe facilities can be seen in Figure 5and was similar in design to the one used at the Westinghouse facility. The fur-nace consists of a brass chamber, approximately 12 by 12 by 18 inches, which iswater cooled by copper tubing brazed to the outside. Sight ports are provided atthe top and side to observe the billet and to obtain optical temperature readings.Inert pa Is admitted to the chamber through copper tubing at the bottom of thefurnace and, if desired, at the might ports. The gas outlet Is at the top of thechamber. Billets are supported on molybdenum pins which are placed into holes ina water cooled copper plate at the bottom of the chamber. This copper plate con-tains an "O"-ring seal and is attached to an air cylinder which raises or loversthe plate.

he induction coil for the high-velocity billets was made by winding copper

tubing into a coil 5 Inches I.D. by 6 inches long. The power supply was a 300 INgenerator operating at 960 cycles. Suitable capecitors were available to balancethe load. The induction coil for the press extrusion billets was made by windingcopper tubing into a coil 3-1/2 inches I.D. by 8 inches long. 2his power supplywas a lO0 KW generator operating at 3000 cycles. Again, suitable capacitors weretailable to belance the load. The water-cooled power leads to the coil enteredthe back of the fdrnace chamber and were insulated from the chamber by Micartablocks. Both col1s were coated on the inside with a thin layer of refractorycaemt.

The teaerature of the billets was raised fairly slowly: first to approx-inately 1200 - iSOO•P, where it vas held for several minutes, then to 2200 - 250OF,and again held several minutes. Finally the temperature was raised to the desiredlevel and held for a minimum of three minutes. Invariably, the desired temperaturewas exceeded. during this tim and the proper adjustments were made to achieve cor-rect billet conditions.

All teperature ueasurefents except for those on the first base-informatlonhigh-velocity billet pf molybdenum alloy, which were made with an optical pyrometer,were made with a tungsten - 100% rhenium thermocouple. This thermocouple was placedInto a 3/16-inch diameter, 3/8-inch deep hole in the billet, at approxiamtely themid-radius position.

Two thermocouples were used to measure temperature on each billet. Temperaturemeasurements were made with a Leeds & Northrup millivolt potentiometer and a milli-volt vs temperature chart supplied by the thermocouple manufacturer, MinneapolisHoneywell Regulator Company.

The time required to transfer the billets from the heating furnace to eitherthe high-velocity machine or the press was recorded and is given in Tables No. 3,4, 5 and 6. This transfer time Is the elapsed time from the moment the furnacewas shut off to the moment the extrusion process started. The relative positionof the furnace and machine is shown in Figures 4 and 5 for the extrusion press andhigh-velocity machine, respectively.

5.* Extrusion Par~ameters

The extrusion parameters used for the base-information high-velocity extrusionof the molybdenum alloy and the tungsten alloy are shown on TRables 3 and 5, re-spectively. Note that these extrusions were made from approximately 3-inch longbillets In the molybdenum alloy an approximately 4-inch lonI billets in the tungstenalloy. The extrusion parameters for the program extrusions for both extrusion pro-ceases) are shown In Tables 3, 4s 5 and 6 for molybdenum an tungten, respectively.Both the high-velocity and press program extrusions were made from approximately14-inoh long billets.

The only parameter that was substantially varied during the program was theextrusion temperature. The other parameters such as tie condition, die steel, andlubrication are merely listed for completeness an were not evaluated for theireffect on either process.

6. 8&a0l.1M and Evaluation Technuiues

Me saMlng tecnqip used. for both the modn aloy and the tungstenalloy for the program press extrusions and high-veloaty extrusions is show inFigure 6. 2he difference in technique was necessary because of the shortness ofthe high-velocity extrusions. A sliht variation was mad. for the tungsten ex-trusions In that slices "A" and "B" were reversed. This was done to obtain amicrographic sample sufficiently far from the nose to obtain worked material. Allsamples for micrographic examination were obtained by cutting the Indicated slicesInto quarters. One quarter was then examined on the longitudinal face from thecenter to the surface of the extrusion. Oxygen and nitrogen samples were obtainedby cutting two 1/4-inch squares from the center of the Idicated 1/8-inch thickslices and were analyzed by the vacuum extraction method. Transverse hardnessreadings were taken on the "D" slice after grinding the faces smooth and flat.This slice was then quartered to provide one of the acrogopbha above, a micro-hardness sample, which was mounted and polished for DPi reainges and two quartersfor recrystallization samples. Four more recrystallization samples were obtainedby quartering the "'" slices. For the molybdenum alloy, these six samples werevacuum annealed for one hour at 250001, 26000o, 2W700F, 280001, 29000• • or 3000.For the tun&'en alloy, five recrystall.sation samples were vacuum annealed for onehour at 27000F, 285007 3000OF, 31500P, or 33000F. All the recrystallizationsamples were subsequently examined for cbanges Sn microstructure.

Tensile specimens were obtained by making a longitudinal cut through the sec-tion indicated. For the molybdenum alloy, all six of the press extrusions thusprovided four tensile specimens each. Only two hih-velocity extrusions, however,were long enough to provide enough material for four tensile specimens. Tensilespecimens used for room temperature tests were machined into standard 0.357-inch

5

diameter specimens with threaded ens. Tensile specimens used for 20000p testswere vachind into special button head upeoimens with a 0.357-inch dIamter gaugesection 1-5/8 inahes long. Half of the tensile specimens were tested in the as-extruded condition at room temperature and at 2000VF. Ens remaining speoimenswere beat treated at 30000F for one hour. This temperature vas chosen becauseresults of the work described below Indicated that 300007 would recrystallize thecold worked high-velocity extrusions. Two tensile specimens were obtained from anas-osut billet. One was tested at room teperature and the other at 200007.

For the tungsten alloy, al•. seven press extrusions provided four tensilespecimens each. Anl high-velocity extrusions provided only two tensile specimens.Tensile test specimens used for rom teuperature tests were machined Into specialbutton head speocmens with a 0.357-Inch diameter gauge section 1-1/2 Iches long.Tensile specimem used for 3000OF were also mohined Into special button headspecimens with a 0.235-inch diameter puge section 1-1/2 Inches long. Ea of thetensile test specimens were tested in the as-extruded condition at room teperatureand at 30000F. So remaining tensile test speolmens were heat treated (vacuumannealed) at 3000oF for one hour. This temperature vas chosen because the resultsof the work described below indicated that 300007 would recrystallize the coldworked high-velocity extrusions. All elevated t•eerate tensile tests were runat the Performence Laboratory of the Westinghouse Central •e•n9)Ser e Dep.rt-ment sid the testing equipment is amply described by Vandebsrgi.tA2

All the prop=. extrusions were photographed In the s-extruded conditionan visualU exmuimed for surface quality.

MFAt I M MUM ALUO! UMS Bt8I8

RIBULTS

Dule Mzforimtion Extrus ions

Bince the major purpose of this part of the Investigation vas to establishthree tepertures wich would produce, respectively, 100% hot work, 100% coldwork, and a structure approximately 50% recrystallized, the evaluation of these"base-information extrusions was limited to surface quality, dimnsions, ead micro-structure.

Sbe surface of the extrusions can be seen In the photogaphs In Figures 7and 8. In general, all the surfaces were smooth and contained few, It any long-itudinal striations or grooves. All the extrulons bad nose bursts, but nowhad any tears or cracks along the length.

The variations in dimensions are presented In Table 7. In one case, thediameter of the bar varied as much as 0.009 Inch from the nose end to the tail end.

Telengths and volumes Increased with increasing temperature,, as did the peam-meter volume per 1000 foot-pounis. Little or no data exist for the parameter forthis molybdenum alloy. Iline(3) reported a value of 0.053 cubic inches per 1000foot-pounds for unalloyed arc-cast tungsten Dynapak-extrudel from 300F at a re-duction ratio of 4:1 On the assumption that molybdenum would extrude ore easily

than tungsten under the sam conditions, the parameter values above are slightlylnoe than would be expected. The differences here might vell be explained onthe basis of the alloy, lubrication differences, and metallurgical differences inthe structure.

Photomicrographs of four of the base-information Dynapak extrusions are shownin Figure 9. ft microstructure of the bar Dynapak-extruded from 2840OF showsapproximately 10% recrystellization. This temperature was, therefore, too high forthe cold working temperature and too low for the intermediate temperature. A barextruded from 3460OF bad a completely recrystallized structure of fine equiaxedains. Further examination of this micrograph, however, revealed a thin layer of

cold worked material at the outer surface of the bar. To remoye this layer, but atthe sasM time not use an excessively high temperature, 3500OF Iaa chosen as the hotworking temperature. Bar number 8070-6, extruded from 27000F, showed a completelycold worked structure throughout the cross section of the bar. This temperaturewas therefore chosen as the cold working temperature. The bar extruded at 2985oFhad a surprisingly large amount of recstallization (80%-90%). On the basis ofthe microstructure of the bor extruded from 28400, and the one above, 2950oF waschosen as the intermediate temperature.

Program Extrus ions

Surface Evaluation

Photographs of the six press extrusions and six high-velocity extrusions canbe seen In Figures 10 through 15. Although sons surface deoal, is lost in thereproduction, the rough surface on the press extrusions is iuediately apparent.This rou1hss was due chiefly to excessive die wear and the subsequent pick-upof die material on the bar surface. All of the press extrusions had transversetears and cracks on the surface, and all had nose bursts which appeared to beworse in the extrusions made from 270001. The two extrusions made from 2700OF hadapproximately 2 inches of fairly smooth surface at the nose end. Although all thepress extrusions had poor surfaces, they could be rated. as follows: 350001, thebest; 295001, Intermediate; and 27000F, the worst.

The surface evaluation of the Dynapak extrusions (see Figures 13, 14 and 15)revealed no silnificant difference in the surface quality of the extrusions madefrom the three different temperatures nor any difference along the length of the"bar. All the surfaces were fairly smooth except for areas speckled with the glasslubricant, and there was no evidence of die material pick-up. All the bars hadnose bursts but none had any transverse cracks. There were evidences of some long-itudinal grooves which spiralled slightly along the length. Ihere was no pipein any any of the extrusions since none of the billets were completely extruded.

Dimensions

fte variations in dimensions of the Dynapak-and press-extruded bars and therequired extrusion energies are shown, respectively, in Tables 7 and 8. The dia-meters of the press-extruded bar varied greatly along the length and, in one case,the difference was as much as 0.190 inch. This large a diameter change was un-doubtedly caused by excessive die wash which resulted from incomplete lubrication

7

during the extrusion process. In addition, much of the die material seized to theextruded bar and further enlarged the diameter.

Te disaeters of the Dynapak-extruded bars, shown In Table 7, varied lessalong the length than did the press-extruded bars. In only one case was the diff-erence between the nose and tail, ends as much as 0.016 Inch. Note also, that inseveral cases the diameter was smaller in the center of the length than at eitherthe nose or tail.

K values for the press extrusions were calculated from the equation,

Pa KlnAoAlwhere Ao Is the nominal reduction ratio and P is the peak extrusion pressure.

r1(Actually, the 8S-A pressure cell and Drush oscillograph unit that was used tomeasure the force did not record, a peak in the true sense. Instead, the york"peak" here means the highest force that was recorded and which usually occurredat the beginning of the extrusion process. In only a few cases did this peakforce differ significantly from the average force exerted during the extrusionprocess.) No K value was obtained for billet No. 80 73-4 because of a milfunotionof the instrument. The K value for billet No. 80 71&-5 Is listed as an estitatedvalue because. the press was not "bottomed" after this extrusion and, as a result,an accurate force value was not obtained with which to calibrate the recorded curve.In general, the K values varied as expected with temperature, and values in the,.range of 60,000 to 90,000 psi are in line with data obtained by Tombaugh, et al)who reported a value near 100p000 psi for this alloy anid similar extrusion para-meters.

K values for the Dynapak extrusions were calculated from the equation,

where E is the Impact energ delivered by the machine, S Is the distance the metalmoves, A Is the cross-sectional area and Ap is the nominal reduction ratio. I in

Althis case is the theoretical energy obtained from the adiabatic expansion of thecompressed. pa rather than the actual energ and is, therefore, necessarily higherthan the actual value. However the K value thus obtained does allow a comparisonof the two processes. Note tha the K values for the Dynapak process are consid-erably higher than those calculated for the conventional extrusion process.

Figure 16 shows more clearly the compar,-so of the K values obtained from eachprocess. In this case, the logarithm of the K talus is plotted against the recip-rocal of the extrusion temperature. The linear relatiozship shown in this figuresuggests that an equation of the type,

K- Ce exp. W

holds for these processes.

The lengths of the bars extruded from both 2700oF and 29500F on the Dynpakwere considerably shorter than expected from previous work. The was caused by achange in the container just previous to the program runs. Rather than 0.005-inchclearance, there was a 0.0l5-inch clearance between the punch and container. Thisdifference allowed spreading and back extruding of the graphite follow blocks, witha subsequent increase In friction along the container walle and reduction In theenergy available for extruding the billet. As a result the parameter volume per1000 foot-pounds was lower for the program extrusions than for the base-Informutionextrusions. In addition, the die bore size was slightly largerp which reduced thereduction ratio and decreased the length.

The difference in die wear that occurred during press extruding and Dynapakextruding can best be demonstrated In Table 9 which shows the die bore diameterbefore and after extruding. The excessive die wear that occurred during press ex-truAding can be seen in Figure 17.

Chemistry

The results of the oxygen and nitrogen analyses taken from the nose and tal.ends of the extrusion are shown in Tables 10 and U. All the values ane low andshow no significant difference between the ends of the bars. Higber oxygen con-tents are shown for the D apsk-extroded bars, but these small differences canpossibly be explained on the basis of original ingot chemistry or by inaccursciesIn analyses performed at low Interstitial levels.

Hardness

The results of the hardness determinations for the high-velocity and press ex-trusions ae shown in Tables 10 ad 11, respectively. Both the tranevers-o andlongitudinal sections show a decrease in hardnes, with Increasing extrusion teep-erature. The transverse hardness of the Dynapak extrusions made from 300F and295•0F are sl&htly lower than the press extrusions made from these temperaturesand can be explained by the microstructure discussed below. Mae difference inhardness between the center and the edge of both types of extrusions an also beexplained by the microstructure, and this Indicates a greater amount of working atthe edge than in the center. 7his fact may only be significant for small extrusionratios such as the 4i:1 ratio used In this work.

Tensile Proprties

Se room temperature tensile test results for the as-extruded material, Tables12 and 13, indicate higher strengths for the press-extruded bars than for theDynapak-extruded bars extruded from the sam temperature. Room-temperature tensilestrengths of 2,500 psi and 92j,00 psi shown for the materhl'press-extruded from270• are slightly lower thsn expected for this alloy. For example, DMIC Report140M indicates an ultimate strength of 105O000 psi for a 1/2-inch diameter rolledbar In the recrystallized condition. The room temperature tensile test results forthe annealed material also show higher strengths for the press-extruded bars thanthe Dynapak-extruded bars. It is interesting to note that the strength values of theannealed material are higher than those of the as-extruded material for both theDynapak- and the press-extruded bars. This fact can possibly be explained by the

9

increased ductility of the annealed material which allows the tensile specimens toreach higher strength levels before fracture occurs. Since many of the specimensbroke in the threads. all the values are subject to question and no valid com-parisons oan be made.

Te button head specimen used for the 2000OF tensile tests did not break outof the gauge length and a more valid comparison can be mds. In this case$ however,little difference is shown between the Dynapik-extruded bars and the press-extruded.bare In either the as-extruded condition or the annealed condition when extrudedfrom the same temperature. Ultimate strengths in the range 14,300 to 50,000 psifor the press-extruded material appear to fall in between data given in DmIC Report140 for recrystallized material at 180007 and 2400F. Figure 18 shows the 2000OFtensile data for as-extruded material as a function of hardness and shows moreclearly the similarity of the tensile properties of Dynapak- and press-extrudedmaterial when extruded from the sas temperature. Note also, however, that at thesame strength level, the press-extruded material is harder; or, conversely, at thesame hardness level, the Dynapsk-extruded material is stronger.

a n lostrrttuie

Photomicrographe taken at the center of the cross section of the six pressextrusi~ons sad six Dympk extrusions are abwn remotively, in Figures 19 and 21.It Is clear, from Figure 19j, that the three chosen extrusion temperatures did not

produce the three desired types of microstructure in the press extrusions. A muchmore cold worked structure was obtained than Indicated by the evaluation of thebase-nformation Dyapak extrusion. Even at 35O000, the press extruded materialwas only approximately 50% recrystallized.

Te photomicrographe of the Dynapak extrusions in Figure 21, however, do showthe desired structures. Material extruded from 35000F consists of completely re-crystallized fine equiaxed gmins. VMterial extraded from 2950oF contains a mix-ture of cold worked and recrystallized grains, and material extruded from 270007consists of a completely cold worked structure.

Figure 20 shows three photomicrographs of press-extruded material. Photo-micrograph. "A" aid "B" were taken at the tail end within I inch of the bottomof the pipe of one of the extrusions made frm 27000?. Photomicrograph "A", whichwas taken near the surface, shlws the expected cold worked structure. Photomicro-graph "B", on the other hand, shows material at the center of the cross section.Here Is revealed undeformud as-cast grains (see Figure 2) which indicate that somedifficulties might arise when using smll reduction ratios, i.e., the surface ofthe extrusion is more highly worked than the center, and some portion of the tailend Is not worked at all. Micrographs taken at t)1A nose end also revealed areasof undeformed as-cast grins. Photomiarograph "C" was Uken at 50X to show thepartial recrystallization that did occur in material press-extruded from 29500P.

Figure 22 shows two photomicrographe of Dynapak-extruded bars. Photomicro-graph "A", which was taken near the surface of the same cross-section shown forthis bar in Figure 21, again reveals the Increased amount of cold work near thesurface of the bars which accounts for the increased hardness values shown inTable 10. Photomicrograph "B" is presented to show the thin layer of cold worked

10

material at the surface of material Dynapak-extruded from 3500OF and the sharptransition from cold worked material to completely recrystallized material. Thisthin layer of cold worked material results from the loss of temperature to thetooling.

Recrs.tallization Evaluation

All specimens, from the press-extruded and Dynapak-extruded bars, which wereheat treated for one hour were examined for microstructure. The moot significantresults of this evaluation are shown in Figure 23 for the press-extruded material,and Figure 24 for the Dynpak-extruded material. Figure 23 shows that only smallchngs occur in the press-extruded material when heat treated for one hour at2900 F. By comparing Figure 23 with Figure 19, slight change in the material ex-truded from 2700OF can be seen in the form of larger cold worked grains, but nosignificant change is evident in the material extruded from 3500 0F.

The microstructures shown in Figure 2A reveal that material Dynapak-extrudedfrom 2700OF will completely recrystallize wben heat treated for one hour at 29000•.When comparing Figure 2• with Figure 21, it can be seen that little change occurredin the material extruded from 29500? an only a slight enlargement of the grainsin the material extruded from 35•0F.

Figure 25 shows the change in hardness that takes place as a result of anneal-iS treatments. In most caes the hardness decreased after annealing, but only thematerial Dynak-extrded. from 27000? shoved a sharp drop near the annaling temp-erature of 290001, aM this was the result of the complete recrystallization dis-cussed previously.

Three significant criteria can be used to compare high-velocity extrusionswith press extrusions. These criteria are: surface and dimensions, as-extrudedmicrostructure, and recrystallization behavior.

7e surface of the extrusions was the first most obvious difference. Whilethe surfaces of the Dynapsk extrusions were fairly smooth aw4 crack-free, the sur-faces of the press extrusions were rough, were covered with die material, and hadtransverse tears along the length. This large a difference in surface quality isnot believed to be inherent in the processes themselves) but instead is due to acombination of Inadequate die preparation and lubricating technique, and the longertime of contact between hot metal and tooling during the conventional extrusionprocess. As a result, the extrusion-press dies washed badly and produced extrusionswith poor surfaces. In the Dynapak process, this contact time is shorter and,although the die preparation and lubricating techniques were the sae as for conven-tional extrusions, die wash was less and the extrusion surfaces were better. Withoptimum die preparation and lubricating techniques for each process, the differencein surface quality and dimensions should be minimized.

A comparison of the as-extruded microstructure indicates that lower hot work-ing temperatures can be used for Dynapak extruding than for conventional press ex-truding. This fact is explained by two differences in the processes: one, the

11

I

working rate and, two, the actual temperature of the billet during the extrusionoperation. In the first case, the working rate of the high-velocity process can

not only raise the tenmerature during extrusion, but can produce sufficient workof high enough stress (at a time when the temperature is still sufficiently high)to cause recrystallitation. [he actual temperature of the billet during extrusionis a function of the rurnace temperature, the transfer time, and the heat loseduring the operation. The first two variables were kept substantially the same.The third variable, however, Is quite different in the two processes. The largemass of the press container and the relatively long time for the extruding operationlovers the billet temperature and thus prevents recrystallization of the workedmaterial.

A comparison of the recrystallization behavior of the extruded material in-dicates that the Dynapak-extruded bars receive a higher degree of stress than dothe press-extruded bars. This is evidenced by the fact that when extrusions arecold worked from the sam temerature on each machine, the Dynapak-extruded materialhas the lowest rearystallization temperature. One would expect this higher stateof stress to substantially increase the hardness and tensile properties. However,this was not the case. A second explanation for the difference In recrystallizationbehavior is the difference in cooling rate between extrusions from each process.In the Dynapak process# where the extrusion was not completed, the extruded barhung in the die and vas air cooled and partially cooled by the tooling. In the ex-trusion press process, the completely extruded bar was imediately placed into anInsulating material, e.g., fuller's earth, weA allowed to cool slowly. This, ofcourse, provided partial stress relief. As a result, a higher temperature is need-ed for recrystallization for the press extrusions.

One other comparison can be made for the lenghe of the extruded bars. Theextrusion press extruded the full lengths of billets used in this program and couldextrude even longer billets. The Dynapak, however, did not completely extrude anyof the billets ands although the correct combination of fire pressures billetlength, and temperature could be determined to completely extrude a billets thereis a definite limit to the volume of material which can be extruded on the Dyapskas there in for all extrusion machines.

PHASE IU 1I ALU= UXMUM IOE

RIULTS

Base Information Extrusion

As for the molybdenum extrusions In Phase 1, thps part of Phase II was db-signed to establish three temperatures which would ptoduce, respectively, 100%hot work, 100% cold work, snd a structure containing approximtely 50 recry-stallization. The evaluation of these base information extrusions was limited,therefore, to surface quality, dimensions, and microstructure.

te surface of the extrusions can be seen in the photographs in Figures 26 and27. The three extrusions from 390&F, 3•IoF, and 3200F had very smooth surfacescontaining very shallow, if any, longitudinal striations. The three extrusions

12

from 3000o0, 28o0)O0, and 2600oF had somew•at rougher surfaces and the longitudinalstriations were more pronounced. All the extrusions had nose bursts which appearedto become worse as the extrusion temperature was lowered. None of the extrusionscontained w transverse cracks and only bar IO 1091 B contained a longitudinalcrack which propagated an appreciable distance. Bars Xr 1091 B and KO 1092 A brokewhile being removed from the die.

The variations in dimensions are presented in Table 14. In most cases the bardiameter varied only 0.004 to 0.006 inch from the nose end to the tal. end. In onecase, bar I0 1092 A, the tall end was 0.015 inch larger. This resulted from thelow temperature extrusion abrading the oxide coating, thereby enlarging the diebore size. The lengths and volumes increased with Increasing temperature as didthe parsater volume per 1000 foot-pounds. Thqse parameter values are higher thanwould be expected from examining data of Kline(3) who reported a value of 0.053cubic inch per 1000 foot-pounds for arc-cast unmaloyed tungsten Dynapak-extrudedfrom 3500OF at a reduction ratio of 4:.1. The higher value reported here might wellbe explained by differences in die preparation and lubrication techniques or bymetallurgical differences in the as-cast structure. The fact that this material isalloyed would lead one to expect a lower value because of its greater resistanceto deformation.

Photomicrographe of the six base Information Dynapak extrusions are shown inFigure 28. The microstructures of the bars extruded from 39000F, 31O00F, and3200oF revealed a completely recrystallized structure of fIne equiaxed grains and340O°F was chosen as the hot working temperature. The miorostructures of the barsextruted from 28000P and 26000? both showed a completely cold worked structurethroughout the arose-motion of the bar, and 2800oF was chosen as the cold workingtemperature. Bar It 1091 A, extruded from 30000?, contained 10% to 00% recry.stallized prains and 3000F was, therefore, too low for the intermediate range.On the basis of this microstructure and that of the bar extruded from 32000F, 310$Fwas chosen as the intermediate extrusion temperature.

Program Extrusions

Surface Evaluation

Photographs of the seven press extrusions and six Dynapak extrusions can beseen in Figures 29 through 31. ITe smooth surfaces of the press extrusions arereadily apparent and are the result of using ceramic-coated dies. All of the pressextrusions bad small nose bursts and a deep pipe at the tail end, but none had saytransverse tears or cracks. They had, however, some longitudinal cracks in the tailend which became less severe as the extrusion temperature was raised. Aside fromthe nose bursts and cracks, there was no obvious difference in the surface appear-ance of the extrusions as a result of extruding from different temperatures.

In contrast with the molybdenum program, the Dynapak-extruded tungsten barshad a poorer surface than the press-extruded bars. All the bars contained long-itudinal striations and all had nose bursts. The severity of the nose bursts ofthe bars does not appear to have any relationship to the extruding temperature.There was no pipe in any of the extrusions since none of the billets were complete-ly extruded, nor does the surface quality change appreciably with extrusion temp-erature.

13

r

ILUltrasonic tests were made on both the press and Dynapak extrusions. The

extent of the pipe and nose bursts In the press extrusions was readily detected andthese areas were removed. Small Indications were revealed In bar IM 1111 A approx-Imately 1/4 inch in from the surface which were removed in subsequent mahinin oftensile specimens. Bar NO 13.09 B contained a creack extending eleven inches from

the tall end. This crack was in the center of the bar and was removed when the barwas longitudinally halved for tensile specimens. Te extent of the nose bursts inthe Dynapak extrusion was readily detected and these areas were removed. On3y twoDynapak-extruded bars had any indication of defects. These defects were very closeto the bar surface and, therefore) presented no problem.

Dimensions

Te variations in dimensions of the Dynapak- and press-extruded bars and therequired extrusion energies are shown, respectively, in Tables 14 and 15. Thediameters of the Dynapak-extruded bars were quite uniform on four of the bars,varying only 0.002 to 0.005 inch over the length. In two of the bars, however, thediameter varied over 0.010 inch over the length. Mie diameters of the prees-ex-truded ban were likewise quite uniform, varying 0.005 inch or les along thelength. Only one bar, IM 1111 B, had a difference of 0.014 inch between the noseend and tall end. The uniformity of the tungsten press extrusions, In contrast tothe mlybdenum extrusions, was due mainly to the ceramic coating used on the dies.

K values for the Dyapak and press extrusions are shown in Tables 14 and 15and were calculated In the same way as for the molybdenum extruions. an teaverage, the K values for the press extrusions varied wivte•, rture as anticipa-ted, and are similar to those reported in the literature ", although soewehat

lower. K values for the Dynapak extrusions also decreased, as expected, with in-creasing temperature. Little or no data exist with which to compa.e these values.Figure 35 more clearly shows the relationship between K values and the extrusiontemperature, and the difference in K values for the Dynapak and extrusion processes.In contrast to the molybdenum curves, the relationship of the logarithm of the Kvalues to the reciprocal of the temperature is not linear. Thie suggests that thes iuae relationihip bbetween K and absolute temperature does not apply here endthat other forces, e.g., frictional forces, are affecting the extrusion pressure.Note also the high K value, 91,200 psi, for billet 1086 B for which the transfertime from furnace to press was 20 seconds.

The lengths of the Dynapak extrusions were slightly shorter than expected fromthe base information runs and is not understood at this time. As a result, theparameter volume per 1000 foot-pounds was also low r than would be expected. Thisparameter, howeverp was still in line with XIine's(3 data.

The extrusion press dies and Dynapak dies are shown, respectively, in Figures36 and 37. Figure 36 shows the fairly smooth ceramic coating remaining on thepress dies with only a few areas "flaked" out. The Dynapak dies, however, hadlarge areas of ceramic coating removed which made it difficult to obtain die boredimensions after extruding. Table 16 lists the changes in the die bore diameteras a result of press extruding.

14

Chemistry

The results of the oxygen and nitrogen analyses taken from the nose and tailends of the extrusions an shown in Tubles 17 and 18. No signifieant differencewas observed between the ingots and the extruded bars or between the press-extrudedand Dympek-extrued bars. No special significance can be placed on the smalldifferences shown In the tables because, although the precision is good (see foot-note 1, Table 1), the accuracy of the analyses at these low levels has not beenestablished.

Hardness

The results of the hardness determinations for the Dynapak and press extrusionsare shown in Ables 17 an 18. Standard steel hardness conversion tables were usedwhere necessary to convert from the scale used to the DPH number. There does notappear to be any relationshIp between the as-extruded hardness and the extrusiontemperature for either the Dynapak extrusions or the press extrusions, nor does theedge hardness appear to be consistently higher or lover than the center. On theaverage, the Dynapek extruzsons appear harder than. the press extrusions. Mheredoes appear to be some evidence that the hardness of the center of the press-extru-ded bar lengths is lower than either end. No hardness readings were obtained atthe center of the Dynapsk-extruded bars because they were too short.

Tensile Prerties

The room temperature tensile test data for the as-extruded material, Tables19 and 20, indicate a higher strength for the press-extruded bars than for theDynapak-extruded bars extruded from the same temperature. 2e linited data andlarge spread in values preclude a significant comparison. The room temperaturedata for the annealed material do not have such a wide spread in values and indicatea higher strength for the Dynapak-extruded bars. In contrast to the tensile testson molybdenum, annealing this tungsten alloy reduces the room temperature tensilestrength and does not Increase the ductility. This is caused by the complete re-crMetallization of all the extrusions when annealed at 30000F (see below).

be 30000? tensile test results reveal little significant difference betweenthe Dy•npak-extruded bars and the press-extruded bars extruded from the sawe temp-erature. Ultimate tensile strengths iAhe neighborhood of 4O,000 psi comparefavorably with data of McKinsey, et al J who reported a vue of 4,500 psi foras-extruded material. A tensile strength of 51p000 psi for the material press-extruded from 2800OF can not be explained at this time.

The changs in 3000OF tensile strength with hardness is shown in Figure 38 which

also shows the increase in tensile strength with decreasing extrusion temperature.

Microstructure

Photomicrog-apha taken at the center of the cross-section of the seven pressextrusions and six Dynapek extrusions are shown, respectively, in Figures 39 and. 41.It is seen from Figure 39 that the three chosen extrusion temperatures did notproduce, in the press extrusion, the three desired types of microstructure.

15

Considerably more cold work appears In the bars exrtrude from 31Q00F and 3h00OFthan would be indicated by the base information Dynapsk extrusion.

The photomicrographa of the Dynapek extrusions in Figure 41,, however, dohave the dom ied structures. Ma!terial extruded from 34I00OF consists of completelyrecrystallized, fins equiezed grains. Material extruded from 28000, consists ofcompletely cold worked grains, and the bars extruded from 310001 contain approx-listely equal amounts of cold worked and recrystallized. gralinsi.

Figure Ie0 shows five photomicrographa at press-extruded material. Picture Ashows the center section of the second tungsten bar extruded from 3)40001 followingrapid transfer from furnace to press., and, shows a greater degree of recrystallize-tion than does bar IC 1086 B for which the transfer tim vam 20 seconds (see Figure39). Photograph B shov the asa bar, but an area, near the aurface - 2here can beseen a greater dogmee of cold work aid fine ricrystallized prains. Photos C and Dane the noise end, and. tall end, respectively, of bar 1111. AD. A comparison of these

two with the same bar In Figure 39 reveals no recrystallization at the nose

end and

Photograph 9 at =O ohows more clearly the recrystallization that took place Inbar KO 1110 B which was extruded from 310007.

Figure I.2 shows four photoomicrographs of Djnapsk-extruded bars * A comparisonof these photographs and those of Figure 141 suggests a bigbier degree of workingat the surface of the bars end. the effect of heat loss at the wose end or theextrusions.* Note the banded structure In photograph C.

Table 21. summarizes the results of the evaluation of the microstructure andshows the greter amount of recrystallization that occurred am a result of Dynapekextruding.

Iscrystallization Behavior

All the spealmons from the press-extruded and Dynipapk-extruded bars were heattreated f or one hour at 270007, 285001,, 30000, 31500, or 330007. Each of thesewere examined. for microstruacture and hardness. Figures 143 and 144 show the mostsignificant result. for the press-extruded end Dympapk-extryded. bars, respectively.Photomicrograph A In Figure t13 shows that sessntially no. recrystallization tookplace In the bar press-axtruded from 28000 and, saesled at 27000P. At 28500?,howevr, a bax extruded. from 28000? becasme completely rearystalllavd. Materialextruded from 311000? completely recrystallized at 30000?, but not completely at285007.

TM photoiolrograsphs of the annealed Dynapak extruasions, In Figure 144, in-dicate that material extruded from 280007 became japproxiiiiately 50% recrystallizedwhen annealed at 2700O7 (photograph A) ami 00% "Mestallized. when annealed at285007. Materia~l extruded from 310007 was appro~4matelY 75$ recrystallized whenannealed at 28500?. Annealing material Dynapsk-ektrudied from 3)40007 merely tendedto enlarge the grain aiite. Compare the prain size in photographs D and E withthose in Figure 141.

Annealing either the press extrusions or the Dynapsk extrusions at 31500, and

16

3300oF effected complete rearystaflization.

A plot of hardness vs annealing temperatures is shown in Figure 45. Althoughthere is a general reduction in hardness as a result of annealing, there appearsto be no discrete decrease Jn hardness with increases in anneaiIng temperature.since the speciumes for this work were taken from identical locations in the ;x-trusions, it would appear that the fluctuations in hardness reflect ingot-to-ingot

DIB=10

ahere are two distinct differences between the high energ rate process andthe conventional extrusion process. One, of course, is the rate of metal vorking.The hih metal working rate of the Dynapek allows less time for beat transfer tothe tools, increases the metal temperature, and appears to inose a higbar internalstress In he terial. e second. difference is the cooling rate of the extrusion.

n the conveional process, the tugsten extrusions are removed from the run-outtable and imediately placed into a trough of insulating material (vermiculite,fuller's earth, etc.), tn the Dyapek process) the extrusion is air cooled becauseIt hangs in the die (in this work) and part of it remains in contact with the die.This difference in cooling rate allows differences In stress relief and, therefore,differences in the state of residual stress.

Noes of the above differences appear to affect the surface of the extrusionswhen proper lubrication techniques are used. n contrast to the molybdenum extru-sens, there was little difference between the surface of the tungsten Dpapsk andpress extrusions. This siamlarity vas due primarily to the ceramic coating usedon the dies. this ceramic coating acted as a heat barrier an, in conjunction withthe gaphite on the die and.glass on the billet, provided sufficient lubricationfor both procesoes. This suggests that equally good surfaces can be obtained byboth processes when the best lubrication techniques are used. Lubrication tech-niques also affect dimensional variations and it appears that equally good diemn-+slonal tolerances can be obtained.by both processes.

The metal working rate and extrusion cooling rate significantly affect thehardness, microstructure, recrystallization behavior, and tensile properties ofthe tungsten extrusions.* For equal extrusion temperatures if the extrusions foboth processes have a cold worked structure, the Dynapak extrusions will be harder,stronger, and will recrystallize at a lower temperature. For slightly higher ex-trusion temperatures, again both being equal, the Dynpak extrusions will be re-crystallized, but in this case the conventional extrusions will be harder andstronger.

Te results of this work suggest that the terminolog "cold work" must befurther defined when discussing metal working operations at elevated temperatures.Both the temperatures of the operation and the rate of metal working affect thestate of residual stress and the subsequent metallurgical behavior and shouldtherefore be stated.. he data also suggest the existence of a powerful tool forcontrolling the hardness level, recrystallization behavior, and, +herefore, theelevated temperature strength of refractory materials.

17

aMORAL COUSI•I8

1. At least twelve cubic Incbes of tbree-Snch diameter are-cast No-25W-O.lZr orW-e60b aloy billets eam be tAd at a a: s red cation rtio ia the oldrworked eAlton an a Model 18o0 t mae 5 voluoe ci be raosedto oaer twenty cubic In aIfhighber extrion temperues axe uieo.

2. T heftcoaloei:y process and the oane•t l exthi sion" soitn p ess produce•qallr and srfagers oextrusione s Goes phuper die preparation, die oating,,and lubricatio tecniques are used.

3. Smw exruio e umperature required., to rek up the an-out grain struct'ure.-into ful recrystal~lized maerial. Is loweer for the h~io-veloe1ty pr'ocessthen for the conventional extuson process.

4. in the cold working temrature reaje the high-veloolty process8 pro:ducesI b~arder and stronger" extr-ston th ba doees the eoaventionsa extrusion process.

5. Was reoptastematten teiiertur*s for h*-veloocty-extruded material ar'lower than those for conventionsly extruded mterial.

1. So extwrusm bS.llets for this vork won all, of as-cast iaterial. 8•a theh1i.-velocity p1,oess aU se rve as a eod3 vorking process as well as aprimar process, the effect of this process an as-forged or extruded materialshould be investigated..

2. A sigifi•ant di.Sfference In substructure may re•ult from arlstieas In therate of metal vorking, an ny be detectede by a sre critical examinationof the microstructure at hioh wlicatioen• .

18

1. Raumannp 0. A., Interim Report 7-882(I), "High Energy Rate Extrusion",UM Aeronautical Systems Center, Westinghouse Electric Corporation -Contract AF 33(600)-49148.

2. Vanderirift, Z. F., "Metal Testing at High Temperatures", AM Publication -Paper mo. 62 - Met 6. April 9-13, 1962.

3. IC.ine, J. A., "Dynapak Extrusions", pamphlet by Convair Division of GeneralDynamics Corporation) San Diego) California, Septemberj 1960.

114. Tombaugh, at a.1 "Development of Optimu. Methods for the Primary Workingof Refractory Metalas" WADD Technical Report 60-:L48, Part In - August, 1963.

5. Houck, J. A.j "Physical and Mechanical Properties of Cotmercial Molybdenum-Uase AllOysB", DMIC Report l140, Battelle Memorial Institute) Columbus, OI±o -November 30, 1960.

6. McKinsey, C. R., *t aX, "Investigation of Tungsten - Tantalum - Columblum -Bae ALloyes"s WADD Tchnical. Report 61-3 - JULy, 1961.

19

---- it .1

II

} a -

20

21*

I ~TRANSVERSE M4ACROSTRUCrTIRE

FIGURE 3 Example of Transverse Nacostructurs and LongigtudinalNicrostructure (IOOX) of As-Cast Tungsten Alloy Ingots.

22

ma

0.8b1a

I, a0L

U0a=

w U

* U.

a -* 4'

U

S*- q.

.0-u0- U

-a.

aIai.

USU.

23

9L

In

wi

24!

L/4 1/8 2-3/4. 1 1 2-314 1. 8 1 4

TAIL H G F D"Aose

Sampling Technique For High Speed Press Extrusions

- - 2-3/4 1/8 1/4.

F D C "

Sampling Technique For Dynapak Extrusions

Code:A. Longitudinal micrographic sample.B. 02 and N2 ga. samples.C. Tensile specimens.D. Longitudinal micrographic sample, micro hardness sample, Rockwell B

hardness, end two recrystallization samples.3. Recrystallization samples.F. ress) Tens~ies.F O an: 02 and N2s sam ples.0. 02 wM N2 gas5 55.UP1e8H. Longitudinal micrographic sample.

FIGURE 6 - Sampling Technique Used for the High Speed Press and Dynapak Extrusions

25

FIBUIRE 'I - loe. Information Dynpaka Extruaion In tle Ac-Extruded Conditlion

26

a-

4u-

0>I~ 070-S8070-6

a-4

FIOUIE 8 B ass Information~ Dynapsk Extrusions In the As-Extruded Condition

27

'0IM

.~ 8.

0!

#071-

8I.,,

F'IUEI ihSedPesEtue as sEtue re20°

f 29

Ij

Il

FIGURE 11 - High Speed Press Extruded Bar*. As Extruded from 290OIF

30

0

Si:t14 11

FIGURE 12- High Speed Press Extruded bars. As Extruded from 3500"F

31

1~

lol

8071-6

FIGURE 13 - Dynapatfoltuded Bars. As Extruded from 2700OF

32

807 1-5

8072-3

FIGURE I4 - Dynapak Extruded Bars. As Extruded from 29500 F

33

r

8069-3

8072-4

FIGURE 15 - Dynapak Extruded Bars. As Extruded from 3500OF

34

564)

353

*075=4 8074,-3

8073-5 B074 -5

807t&-4 8075° I

FIGURE 17 - High Speed Press Extrusion Dies After one Ei.trusion of theBillets Indicated

36

1.10.

0 &1

NU

IoniIN 601HDII-IA-1i

37z

IVI

W141 14IJ

FIUE1 -LniudnlMcrgah O O)ad xrdngTmeatrso

High~ ~ ~ Spe rs xrddMoydnmAlyBr

38

80738511 6073-511

j-4

Oft I-5

C

FIGURE 20 -Longitudinal Micrographs of High Speed Press Extruded

Molybdenum Alloy Bars

A. Tail End Near Surface - OOXB. Tall End at Center of Cross Section - OOX

C. Same as Micrograph In Figure 14I, but 50OK

39

. . . . .. . . .. . . ---

FIGURE 21 -Lovig Itudinal Micrographs (IOOX) and Extruding Temperatures ofDynapak Extruded Molybdenum Alloy Bars

40

S~ 807 i-BE

A

800.-SE

S,

FIGURE 22 - Longitudinal1itcrographe (1ox) of Dynapak Extruded MolybdenumAlloy Bars

A. Area Near Surface of Extrusion from 2950OF

a. Area Near Surface of Extrusion from 3500WF

4:L

P;7 8073-SE29

S~2700°F

4 .1

807114-'E29

3500OF

FIGURE 28- Longitudinal Micrographs (IOOX) and Extruding Temperatures of HighSpeed Press Extruded Molybdenum Alloy Bars Heat Treated for I Hour at 2900'F

42

IJ

8071-SEtS SO? 1-SE29

27000 F 2950OF

FIGURE 24 Longitudinal M~icrographs (lOOX) and Extruding Temperatures ofDynapah Extruded Molybdenum Alloy Bars Heat Treated for I Hour at 29000F

43

- -11 -6SNGV

122

/6 10

-i iA-N

44 CO

AA

Idn

- - -- - - - - -

4m3 !TMu'553NbwV

"I -II

KC I OBBBECS108A. 8200°F

"~C I 085AoB440OF

KIC 108

39004F

FIU RE 26 - Base Information Dynapak Extruded Tungsten Alloys Bars. As Extruded

from the Indicated Temperatures

45

KC 1091A KC 10916 KC 1092A30000 F 2800OF 2600OF

FIGURE 27 - Base Information Dynapak Extruded Tungsten Alloy BarsAs Estruded from the Indicated Temperatures

46

ISMA0M

.... ..

FIWJRE 28 Longitudinal Micrographs (tO0X) and Extruding Temperatures of

ease-informationl Oynpaps Extruded Tungsten Allay tars

417

S!

KC IIIOA KC I o10s

FIGURE 29 - High Speed Press Extruded Tungsten Alloy Bars.As Extruded from 2800

0F

48

II

KC IIIIA KC IlOS1

FIGURE $0 - High Speed Press Extruded Tungsten Alloy Bar*.As Extruded from 5100

0 F

49

r,4

I 'j

44.•

KC 1086A KC 1V86B KC 11118

FIGURE 31 - High Speed Press Extruded Tungsten Alloy Bars.As Extruded from 34O00F

50

-

I¢

I 1

KC 11058 •XC JI oA

S-"FIGUR E1 - Dynapsk Extruded Tungsten Alloy Bars. As Extruded frem 2800F

51

XC 1104A

KC 1lOUD

FlUKE 832 Dynapak Extruded Tungsten Allay Bra. As Extruded from 3100*F

52

rjrL

1 .4w

KC 11083 KC I108A

FIGURE $4 - Dynspak Extruded Tungsten Alloy Bars. As Extruded from 3S00°F

53

- - - -

2 UU£

-- - I -Ix iI*�

I. §1'-* __*

4 *�i___ 1'-

1� I �:-t--- ��1� I.-

�jI'I 3,

K

I 'I wI �I mI0 IL

- - - - - - - -B 2

lOd 0001 'C�6) .LNYLSNOO N0ISfl�LXU

54

XC 1093 xKC 1IIIA

I 1 I1I1A KC IOSSA

KC 11101 KC IO86B

FiIRE 38 - High Speed Press Extrusion Dies After One Extrusion of the TungstenAlloy Billet Indicated

55

FIWURE 27 -Dynapaki Extrusion Dies after one Extrusion of the TungstenAlloy Billets Indicated

56

II�____-

____ ____ ia. ___ -1I

_________ _________ =I IS

LOo -

q*. -

S-v-liI'?

4'

z Ii

I-.

iiS

-S.85

UU

U.

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lime-11C 111O-0

FIBIRE 89 - Longitudinal Micrographs (b0OX) and Extruding Temperatures of HighSpeed Press Extruded Tungsten Alloy Bars

58

MiA otro aaLm reP ! I

A - hasr INa aso f Cros btwwud hmU - I=S

I - Is. 9 tadt floster of gross Beetlom - 10OU

I - Use as fllcrogveuti Is "ret3,asR bat NOOR

FIGURE 40 Longitudinal Mlicrographs of High Speed Press Extruded TungstenAlloy Bars

59

;k~

FIGURE 41l - Longitudinal Micrographsa (IOOX) and Extruding Temperatures ofDynapak Extruded Tungsten Allay Bars

60

f

|0

J 7

99 " Is a15I-I EI e1m,.4C

A - Area Near Surface of Bar Extruded from hIOOOF

8 - Nose End at Center of Cross Section of Bar Extruded from $100oF

C - Area Near Surface of Bar Extruded from 8N00*F

0 - Nose End at Center of Cross Section of Bar Extruded from $1O,0F

FIGURE .2 - Longitudinal Micrographs IOOX of Dynapak Extruded TungstenAlloy Bars

61

CONA - A0001al On Bee er 17N*F11-- Anemaled One bar Isnooo*Asesealed Noa "or 2worI - Anesaled 0" Near *UWFI - Annealed San Near 2110Pl

Sio

8400' F

FIGURE '15 Longitudinal Micrographs (10OX) and Extruded Temperatures of High SpeedPress Extruded Tungsten Alloy. Bars Heat Treated for One Hour

62

I:

lbe? I 8"*

I -Asmeald lee fter 8*WV

. I IFIGURE 4 - Longitudinal Hiorbgraphs ~IOOX) and Extruding Temperatures of Dynapak

Extruded Tungsten Allay. Bare Neat Treated for One Hour

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