_: ·r

J. ~lal~r.-E.r~~.-(1989) 11:45-49

_385-!:~

iC IlJR9 SJlrlll~er-VcrlJlll Ne't\" Yorik

Effect of Annealing on MagneticProperties of ~-'e-47.5 %Ni AlIoy

Fernundo José Gomes Lundgruf, Hávio llencduceNeto, Duniel Rodrigucs, Gilberto Concílio, und

Ronuld Lesley Plaut

Abstrnct. The cflecl of unnculing IClIlpcralure on g(';lin size. lllaXillllllll pdrllleability andcncrcivc force of 47.5% nickcl-iron ull()ys with difTcrenl slIlfllr contents was investigated.Alloys wilh lowcr slIlfllr contcnl reqllirc lowcr unncaling telllperalurc 10 ullain spccifieu values(lf lllagnclic propcrtics. The l'XpcrilllCnlul reslllts show IIHltlhe cocfficicnt 3"1/M,. whcrc "y

is the uOllluin wall enl'rgy uml M, ls lhe saturation Illagnelizalion. can bc llseu 10 corrclalebolh coercivc force and IllUXillllllllperlllcubilily 10 grain sizc.

INTRODUCTIONa constant, indcpendent of grain sizelhe domain wall ellergy, 11m2lhe saluralíon lIIugnelization, Tlhe grain sizc. m.

WhereA

"(

M .•d

Those aUlhors 14] showed thal lhe constanl ;\ eanne associaled with the Ilolllllelallic inelusiolls prescnlin the alloy. While Collíng and Aspdcn 151 round del­etcrious cllects due to lhe presence 01 sulfur and ox­ygen, Adler and Preiner did no! confirlll such a re­lalion, establishing that only those incJusions wilhdílllensions close to the domain wall thiekness (0.02­0.05 J.llll) affect the cocrcive force.

In lhis paper. materiais with diflerent sulfur con­lents are investigated in ordcr to evaluate lhe grainsize elleets in alloys with diflerent volume fraetionsof inclusions.

The eoefTicient 3"{ IM, was used by Adler andPfeifTer 14 j to correlale grain size and coerei ve forcethrough DÜring's model 19) of lhe magnetie fieldstrength necessary 10 promote irrcvcrsible dornaín wallmolion. It has been shown to bc valid !o express thep,rain sizc effecl of rure iron tIO\, 47.5% nickel-iron141. Ni-Fe-Mo-Cu alloy 1111. and Nd-Fe-B mag­nets 112/.

Adll1itting that the maximurn perrncability is alsodependenl on irreversiblc domain wall molion l13 J

we díseuss here the possibilily of expressing lhe effecor grain size using lheorelical relatim,!" between max­11llUlll permcability anu coercive force 1141. Experi-

(I)H r = A + 3"( . (!)M. d

ç ,·';lh IPTjDIMET. Av. PlUr. AlllIeiou Praoo.;':'._~--i:i. San (Sao) Paulo, Bru:r.il.

The l1lngnetic properties af the 47.5% nickel-íron al­lo)'s are conlrolled by the chelllical cOlllposition lI\,

mechanical warking 121. and the final annealing 13 j.The efrec!s or thcse mctnllurgical proccssing sleps

. ',<H-eheen interpreted in tenllS ar the interaction 01'

ilagnctic dOlllains with microslruclurul churacleris­iC'S. such riS grnin size 141. inclusions 151. and texlure:'J. The behnvior of the domains is !lIso inflllenccd

.nsic magnetic propcrl ics sllch as magneto-.}""5illllineallisotropy and magnetostrktioll. which are

ecled by these processing variables 11,21.

e fmal annealing affects not only grain size butvC-ll1entianed charactcristics, and has becn

LI)" invesligalcd in lhe litcraturc Il··-R I. The;-:-e5:~~:'p~per shows experimental elfeets 01 lhe an-

g lempernture on de cocrcive force and rnaxi­eability ar the alloy. searching lor n rela­

'- ::fn lhe grnin síze resulting frorn lhe annealingerties.

. Pfeiffer 14) have shuwn lhat cocrcivc force_5: :neter) can be related to grain síze by lhe

r· .." .

J. Mulerluls EIl~illeerillg, VIII. 11. No. I, 1989

-

SYMBOL'AO<>

QO

Sppm

esoeso301080

1000 10150 1100TEMPERATURE

180

ALLOYA

BCD

E

o

o

LtJ(.)a::OLI..

Flg. 2. de coercivc force as a funcl~n of annealing tem­pcrature (4 hr eyclcs).

cocrcive force, llUJ ITlllximurn perrncability. Thesefigures show Ihat lhe increase of annealing lempera­ture and the reduction of sulfur content optimize themaguclic propcrtics of thc alloy.

l11C carbon conleut 01' lhe salllples dropped to less

than 50 ppm in ali annealing cycles, bUI it was nolpossible to detect a variation of the sulfur eonlentgreater lhan 10 ppm using the infrared-detection COffi­

bustion melhod.

It should be noted in Figures 2 and 3 that the an­nealing temperature necessary 10 obtain ASTM spec-

980 !~OOO 10fSO 1100 liSO

TEMPERATURE tOe)

I<'IJt. l. Grnin size as a function of anncaling temperalure(4 hr cyclcs).

Ê'"cl-

100

z 200-cln:e"

llJN 300-CI)

4I4

44

4I4

Timc (hr)

950

10501050

1050roso11001150

1150

Tcmpcralurc ("C)

Tllblc 2. Annculing I'urumctcrs

- '. 2. and 3 show lhe effects of annealing tem­d sulfur content of the ingots on grain size,

c:

1. Chcmieal COlllpositi~n of the Alloys

%Mn

%Si%C%S%0

0.38

0.150.01500050.0030.39

0.140.0160.0050.003O.3R

0.130.021oom0.0020.38

0.130.0260.00 I0.002-

"- ..•.. -0.390.150.0130.0050.002

of 47.5% nickel-iron alloy wilh different(Table I) were melted in a vacuum

ace. The ingots were hot and cold rolled.reduction of 85%. l'his reduction is some-

inferior to lhe limit ar 90% •. nbove which the

~ of~condnry gruin growlh und strong tcx­expected after annealing l2J. Strips of

::nckness were stamped to obtain ring speci­-~- (,.l;""'ensions of 50 x 40 x I mm) for magnetic

annealings were done (Table 2) undcr:: ....•"Ogert Jtmosphere with n dcw poinl of - 35° C, to

erences in grain size.

_.~~e::ic rneasuremenls in de condilions were per­ilh a hystereslsgraph l15 J. rcsulting in theforce nnd mnximu11l perllleabilily vuluesfigures 2 and 3. The coercive force wasrom a maximulIl induelion of 1.0 T.

1Fc::i:m;ng lhe procedures of Adler aml Pfciffcr 141.

iz.e of annealcd samples wns lIleasurcd bymelhod, counting lwins as intcrfaces

-- t.o grain boundaries.

~l:LTS

EXPERL\lENT AL PROCEDURES

F.J.G. Landiral' et ai. • AnllcallllR und MOlllctlc: l)rupcrtlcI ur .'c-47.5%NI

mental resulLS are eampared with theoretical fore­casLS.

46 • J. !\1aterials Englneerlllg~ Vol. lI, No. 1,1989

,.\ :...~ll-

F.J.G. Lundgrar et ai •• Anneallng aild Mugnctlc Properlles or Fe-47.5

B

270

270

300

220300275

290

290

5.1

4.7

3.12.53.6

Table 3. Linear Regression Coefficients of the RelationBctween Coercive Force and lhe lnverse of Graio Size.

Compared to Theoretical and Experimenlal Values'

Alloi} .. A

A

B

COEMcun vuluc

Thcorcllculh

Experimcntal'

Correlntion Between Grnln Slze andMnxlmum PermeabilityThc experimcntal results presenlcd in Figures I and3 showed a relation bctwccn grain growlh and the in­crcase 01' maxill1ull1 pcrllleability. Chikazumi 114J

showed lhat both maximulII permcability and coereiveforce can be relaleu 10 lhe critical field strength (Hg)

for irreversible domain wall motion through Eqs. (2)and (3) bclow, in materiaIs with cubic magnetocrys­lalJinc unisotropy and a random elistribution of grainoricntalions:

'U, '" A + B(lld), where d i5 grain size (I-l-m)hHcfcrclIcc 121.

'Rcfcrcllce [4J.

SYMBOLti.OO'QO

Sppm

150

150

~o10150

ALLOYA

BC

O

E

L1000 10tlO - 1100 11tiO

TEM P E R A T U R E (OC)

pcrnlcability vs. annealing lcmpcrature.ults are slightly shifled for clarily.)

o

- .CD

.c:tlJJ

~a:\.LI

~

_ 12fi)O

::. '100•'~.~--~~. ~.-i"- .• i< _. O' .J

(2)

(3)/f, = 1.2lf~, A/m

0.5/J,J-Lmu "" --- (auimcnsional)

J-Lo/f ~

IJ.O = 41T X 10-7, H/m

lJ, = saturation inuuction. T

where

j of magnelic propcrties is elcpcllelcnl00 Ule r"':":nr cootenl af lhe ingot.

es not shaw a c1ear retalion between

sulfur OOill:em and grain sizc, which mighl bc ex­pectoo ir lhe laller were delermined by the volumef raction Q~ inclusions 116 J. The occurrence or sec­

Ilization, detecleel in the samples orAlio}' B anncaled aoove 1000° C, indicale lhal other

, ·~.r-rcrcd wilh lhe grain groWlh.

DISCUS-SI01\

COlllbining Eqs. (2) and (3), a relation betweenlIIaximum pcnneabilily anel cocrcivc force ean be foundunu cvaluulcd for a 47.5% nickcl-iron alloy (8 J =1.55 T).

E fTecIt of Grain Slze 011 Coerclve FOI'ce

The experimental values of cocrcive force can be re­

laled [o lhe Lnverse of grain size, und Tablc 3 shows

lhe value:s af Lhe conslant A anel lhe lIngular coeffi­cienl obta:ioed with linear regressions relaleel to eachalloy. TO.e results show thal. while conslanl A de­pends ao lhe sulfur conlenl of lhe nlloy, lhe angularcoefficient ma)' not have thal uepenucncc. 'rhe av­erage value af lhe five alloys is similar to the theo­retical and experimental values shown in lhe lilerature12,4J.

J-LO /f,,,-I = = 1.35 x 10-6. H (udirncnsionaJ) (4)"'.Ia, 0.58, 1.2 '

Figure 4 shaws the experimental fit to such a linearrelalionship. The conslanls are given in Eq. (5). ItseXlrapolulion eloes nol cross lhc origino which maysuggest that lhe irrevcrsiblc movemcnt of domuin wu11s

is nol lhe only mechanism operaling in tj1is material.The sll1all differcnce observed belwçel1 calculaled andll1easured valucs of lhc slope suggcsls the applicabiJ-

J, Mllteduls Enl:lncerllll:, Vol. 11, No. I, 1989 • 4

,;.r;-ir:-O-:J1I, ..~ - ~.~\:itJ~ ·Ii·'·· - -_

(7)

(6)

3.93.34.3.65.l

1.3U0.90.670.95

(3'Y) = q' O.Gil, X 10-6M, up ILO

I 1-\00 ( 3'Y IO~) (I)1-\0;••• = -- A' + - . - = p + q -

0.68, M, d d

AUCDE

Alloy

Tohle 4. Linear Regrcssion Coefficicnts from lheRelalion Bctwccn Grain Size and Maximum Permcability

from Eq. (6)

o e 10 15 20 25 30

INVERSE OF ~GRAIN SIZE (p..m-l) (10-5)

Tablc 5 shows lhe valucs for each alloy. cornparcdto the value calculaled using B, = Ms = 1.55 1and

the domain wall energy estimated by Pfeiffer et aJo

where d = 1.1.111.

The experimcntal results shown in Figures 5 and 6ean be fitted to sue h a linear relalion, giving rise to

the caefficienls p and q presenled in Table 4. Onceagain. the grain size dependent coeffieient shaws nodcpcndence on sulfur content, unlike constant p. lheangular cocllicicnt can be used to produce experi­mental values of the conslant 3'V/M, (ampere):

.'Ig. 6. MUXlrllUIIl pcrlllcabilily U~ a funclion of grain sizefor olloys wilh dilTcrcnl sulfur conlcnts.

2.!5

rpt~..52 2

-T~C'l.!5e::t.. I~o~ ~<> c

O E'Q o

6 AO B

O E

6 AO B<> c'Q OO E

imum penneabilily as u funclion of grain size=- equa.l sulfur contenl (50 pplll).

~ht.B'lah Englnccrhtjl, Voto 11. No. I, 1989

c

o

ity of this relation between maximulll pcrmeability andgrain size.

Expcrhncntnl Rclntlol1s IJetween (;ruln Slzeand Maxlmum PermcabllltyThe combination of Eq. (4) and Eq. (I) offers a re­latian between maximum permeability and grain size,as given in Eq. (6).

2

48·

FtR. 4. Relalion bctween coercive force und lhe inverse ofmB..'iti mUIll penneabllllY.

-10

F..J.G. Landgrat d aJo • AnncollnR ond Mugndlc: f>ropcrtles or "'e-47.5%NI

--10IO

,.

----~--~_.- ~\~~; ~,~-;.. ~~ (, .. • _ ~:t-~ ".•...

,to

an experimental constant for each aHoythe gruin size, l1l

I. a. CouJcrchon IIml J.F. Tícrs. Jourt/a/ of MagnelÍ.lm

alld MCl811eticMateriaIs. 1982. vo!. 26, pp. 196-214.2. F. Pfeifer Ilnd C. Radcluff. JOIlrf/al of Maglletism and

Maglletic Mmrria/s. 1980. vol. 19. 1'1'. 190-207.3. W.S. Elx·r1y. Metal.f EII1(illeerinR Quarterly, 1971. vol.

11. pp. 40-47.

4. E. AJlcr Ilnd 11. PfcilTcr.I/EEE Tralls. Mag., 1984,vo!. 20. pp. 1493-1495.

5. D.A. Colling uml R.G. AspJen. J. Appl. Phys .• 1969,vo!. 40. 1'1'. 1571-1572.

6. R.T. Casanl. W.A. Klawittcr, A.A. Lykens. anJ F.W.Ackcrl11llnn.J. App/. Phys., 1966. vaI. 37. pp. 1202­1204.

7. W.A. Klawillcr and A.A. Lykcns, 1'rOllS. ASM. 1964,vol. 57. pp. 3M-36X.

8. M.J. Savitski, J. Appl. /'hys .. 1958. vol. 29, pp. 353­355.

9. W. Diiring: Zl'it jilr J>hys.. 1938. vol. 108, pp. 137­152.

10. A. Mager,A",1. derJ>h\'s., 1952, vol. li, pp. 15-IR ..11. F. Pl"eifer alld W. KUI·IZ.JOIlrf/al of MaWll'liJm alld

MaRlletic Material.l. 1977. vol. 4, rI'. 214-219.12'. W. Ferncngcl. Fíl'lh Inl. Symp. un Magn. Anis. and.

Coerc. in R.E.-T.M. Alloys. 1987. pp. 259-265.13. S. Chikllzullll. f'lI.vsics 01' MaRlletism. Johri Wilcy Co ..

Ncw York. 1%4, r. 245.14. S. Chíkawllll. l'hy.fies /JI' MaRlletÜm. John Wilcy Co ..

Ncw York. 19M. p. 294.15. F.J.G. Landgraf: Maslcr Thesis. p. 69. EPUSP. São

Paulo. 1987.

16. 11.1'. Sluwc, ill F. Hacssller eJ. Recry.lwllizatioll vIMetallic M(/ferials. p. 19. DI. Reidercr V.• Stullgart .1978.

17. American Socícty for Tcsting and Materiais: Nickel­Imn Soft Ma/:"etic Alloy.\. A 753-85. 1985. vo!. 03­04, see. 3.

A" =d =

The oc~urrence of lcxturc associatcd with seconu­ary grain growth interferes with lhe rclatian between

grain size and lllaXilllllnl pcrmeability, worsening thefit 10 the above exprcssion.

REFERENCES

2.9

2.43.52.7

3.8

3.00.52.86

F.J.G. Landgraf et ai. ~ Anneallna and Mllgllctlc: Propertlel of Fe-47.5

.68, [ 3-y (I)J-I=-- A"+- -

tJ.O M, d

10-' J 1m2• The COI11(lllriSOllsllows Ihllled to n good npproxilllatioll for the

eeo g:rain size and maximum pcrmeabil­fit, Alloy B, might be explained in

ocrurre:nce 01' sccondary gmin growth wilhr n (I t 2) texlurc. probably due tothe last slage aI' hot working.

e annealing tClllpcraturc prolllotespenneability and lawer cocrcive

~ gmin growth frolll 30 11111111900" C50~C.'ent 01' the alloy makes an ill1portant

coercive force :md IlInXillllllll per­with lower sulfllr conlent rcquire

el11perature to allain the specifiedngnetic propertics.

~:t;rrimental reslIlts confinn the rclation pro­l. 141 bctween grain si7.e and coe r­

Iso possible to cstnblisll a rclation.• and maximum permeability by the

~

Alio)'

l31. as I.Eq. t6relalio

ity. Thetemthe dework

,'- .., '-.

-.. '- -:-. :-~l.~"~<.l-f~,...- " ".- ~;~€'-

Table 5. Experimental and Theoretkal Valucs of 3-y/M.

J. MaterIais Enl:lneerlnl;. Vol. li, No. I, 1989 • 49

Volume 8, number 11.1 ~ MATERIALS LETTERS November 1989'-

EJ

NEW STABLE PHASE 1N THE BINARY Fe-Nd SYSTEM 3.

G. SCH:\EIDER 3.1.

r:

IrfornNd.in fanar600dTthe'

[ S,e­

trannea!nealNd;

MobtatioO'

this,sho\\slowcouro

Fel7

eratcrich

TIfact

The al!oys were prepared in the form of 2-3 g but­tons by arc-melting under an Ar atmosphere. Theywere then wrapped in Ta foil and sealed in Ar-filledquartz glass capsules to be annealed at 600°C for thetimes mentioned in the text. The purities ofthe start­ing materiais were: iron, 99.98% and neodymium,99.9%. The oxygen content ofthe starting materiais,measured with a leco gas analyzer, was: iron, 390ppm and neodymium, 350 ppm. For the X-ray dif­fraction patterns, we used a Rigaku diffractometerwith 28 scanning. Magnetic measurements were per­formed with a vibrating sample magnetometer as de­scribed in refs. [5,6]. DT A measurements were madewith a Netzsch 404S differential thermal analyzer.EPMA measurements were made with a lEOl 840A

2. Experimental

Induslrial, CEMAR. Brasil'niversidade de São Paulo, c.P. 20516, São Paulo. SP., Brasil

\'. \'IL...~..s-BOAS, G.H. BEZERRA, F.P. MISSEllUniversidade de São Paulo, c.P. 20516, São Paulo. SP., Brasil

',-eO 16 August 1989

.~::r=" ,·r.sll!U!e, UlliversilY of DayLOn, DaYloll, OH, USA

F.J.G. L-iL."DGRAF

11lSIIiU;O~?Pcs;;-:Jisas Tecnológicas do Estado de São Paulo, São Paulo, SP., Brasil

An invesligation of binary Fe-Nd alloys revealed lhe existence of an oxygen-free, stable Fe-rich phase Az, forrned perilectically

in the range 750-800°C. EPMA shows this phase to contain 22.8 at.% Nd. This ferromagnetic phase has T,=230°C, bul lhe

samples presentlow H, values. The X-ray diffraclion pattern can be indexed using a hexagonal cell with a = 2.021 nm and c= 1.235nrn.

Renewed interest in an article by Drozzina and

[ I ], reporting high coercivity in as-cast Fe-Nd··OY5. nas revived the discussion about the number

,E' ;:Ü:ases present in binary Fe-Nd. Several authors:=-5: h2\'e characterized the metastable phase with:c=2':.s=C. which we referred to as AI' 1nvestigating:Í1::- s-:a~i;~·.:--af this phase, we found a second phase'.: •...,-:~ =-::= 2::0=C in a Fe-Nd specimen which had

r=::'::- ••.. ::-::. a :Jag annealing treatment [6]. 1n this pa­;.;cr ~ c ;:::3:=;:: :hase properties of A2 which are wel!­:=s-..E,j~:~::-::' ~: :;':'.epresent time. We show this phase:0 ~ ~:;.:ZI :0 ;:>naseswhich, in the literature, have

oxygen stabilized [7,8].

1. 1ntroduction

Fig.. I.inler.-::

472 o 167-577x/89/$ 03.50 © EIsevier Science Publishers B.V.

(North-Holland Physics Publishing Division)