Effect of annealing on the magnetic properties of Fe

_: ·r
iC IlJR9 SJlrlll~er-VcrlJlll
J. ~lal~r.-E.r~~.-(1989) 11:45-49
Ne't\" Yorik
_385-!:~
Effect of Annealing on Magnetic
Properties of ~-'e-47.5 % Ni AlIoy
Fernundo José Gomes Lundgruf, Hávio llencduce
Neto, Duniel Rodrigucs, Gilberto Concílio, und
Ronuld Lesley Plaut
Abstrnct.
The cflecl of unnculing IClIlpcralure on g(';lin size. lllaXillllllll pdrllleability and
cncrcivc 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 corrclale
bolh coercivc force and IllUXillllllllperlllcubilily 10 grain sizc.
Where
A
INTRODUCTION
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 but
vC-ll1entianed charactcristics,
and has becn
LI)" invesligalcd in lhe litcraturc Il··-R I. The
;-:-e5:~~:'
p~per shows experimental elfeets 01 lhe ang lempernture on de cocrcive force and rnaxieability ar the alloy. searching lor n rela'- ::fn lhe grnin síze resulting frorn lhe annealing
erties.
. Pfeiffer 14) have shuwn lhat cocrcivc force
_5: :neter) can be related to grain síze by lhe
Hr = A
+ M.
3"(
.
(!)
d
(I)
ç ,·';lh IPTjDIMET. Av. PlUr. AlllIeiou Praoo.
San (Sao) Paulo, Bru:r.il.
;':'._~--i:i.
"(
M .•
d
a constant, indcpendent of grain size
lhe domain wall ellergy, 11m2
lhe saluralíon lIIugnelization, T
lhe grain sizc. m.
Those aUlhors 14] showed thal lhe constanl ;\ ean
ne associaled with the Ilolllllelallic inelusiolls prescnl
in 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 wilh
dílllensions close to the domain wall thiekness (0.02-
0.05 J.llll) affect the cocrcive force.
In lhis paper. materiais with diflerent sulfur conlents are investigated in ordcr to evaluate lhe grain
size elleets in alloys with diflerent volume fraetions
of inclusions.
I
The eoefTicient 3"{ M, was used by Adler and
PfeifTer 14 j to correlale grain size and coerei ve force
through DÜring's model 19) of lhe magnetie field
strength necessary 10 promote irrcvcrsible dornaín wall
molion. It has been shown to bc valid !o express the
p,rain sizc effecl of rure iron tIO\, 47.5% nickel-iron
141. Ni-Fe-Mo-Cu
alloy 1111. and Nd-Fe-B
magnets 112/.
Adll1itting that the maximurn perrncability is also
dependenl on irreversiblc domain wall molion l13 J
we díseuss here the possibilily of expressing lhe effec
or grain size using lheorelical relatim,!" between max11llUlll permcability anu coercive force 1141. Experi-
J.
"r· ...
Mulerluls EIl~illeerillg,
VIII.
11. No. I, 1989
-
F.J.G. Landiral' et ai.
mental
resulLS
•
AnllcallllR und MOlllctlc: l)rupcrtlcI
are eampared
with theoretical
ur .'c-47.5%NI
fore-
S
ALLOY ppm
casLS.
A
B
C
EXPERL\lENT AL PROCEDURES
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 someinferior 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 the
force nnd mnximu11l perllleabilily
vulues
figures 2 and 3. The coercive force was
rom 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 by
melhod, counting lwins as intcrfaces
-- t.o grain boundaries.
~l:LTS
- '. 2. and 3 show lhe effects of annealing temd sulfur content of the ingots on grain size,
..•.. 0.39
%0
oom
0.00
0.005
%S
0.15
0.013
0.002
0.026
0.13
0.021
%Si
%C
0.016
0.14
0.015
0.003
0005 I
1. Chcmieal
Q
80
E
N 300
10
<>
O
CI)
z- 200
cl
n:
e"
100
o
980
!~OOO
10fSO
1100
TEMPERATURE
I<'IJt. l. Grnin size as a function
liSO
tOe)
of anncaling
temperalure
(4 hr cyclcs).
cocrcive force, llUJ ITlllximurn perrncability.
These
figures show Ihat lhe increase of annealing lemperature and the reduction of sulfur content optimize the
maguclic propcrtics of thc alloy.
l11C carbon conleut 01' lhe salllples dropped to less
than 50 ppm in ali annealing cycles, bUI it was nol
possible to detect a variation of the sulfur eonlent
COffigreater lhan 10 ppm using the infrared-detection
bustion melhod.
It should be noted in Figures 2 and 3 that the annealing temperature necessary 10 obtain ASTM spec-
"-
COlllpositi~n
-
llJ
A
O
30
D
SYMBOL'
eso
eso
of the Alloys
%Mn
Ê
'"
cl
LtJ
(.)
a::
O
LI..
Tllblc 2. Annculing I'urumctcrs
c:
Tcmpcralurc ("C)
Timc (hr)
950
4
I
1050
4
4
1050
1050
46
•
J. !\1aterials
o
180
1000
10150 1100
roso
1100
1150
4
4
TEMPERATURE
1150
4
Flg. 2. de coercivc force as a funcl~n
pcrature (4 hr eyclcs).
I
Englneerlllg~ Vol.
lI, No.
, :...
.\
~ll-
1,1989
of annealing
tem-
F.J.G.
Lundgrar et ai ••
Anneallng aild Mugnctlc Properlles
or Fe-47.5
Table 3. Linear Regression Coefficients of the Relation
Bctween Coercive Force and lhe lnverse of Graio Size.
Compared to Theoretical and Experimenlal Values'
_
fi)
12
Alloi} ..
O
A
B
•'~
. -~.-i
::.
'
"- .• i<
'100
.~--~~
.J
_.
.
C
O
E
O
B
A
5.1
270
4.7
270
300
220
300
3.1
2.5
3.6
Mcun vuluc
Thcorcllculh
CD
275
290
290
Experimcntal'
.c:t
lJJ
~
'U, '" A + B(lld),
hHcfcrclIcc 121.
'Rcfcrcllce
[4J.
a:
\.LI
~
ALLOY
o
S
SYMBOL
ti.
O
ppm
A
150
B
150
C
~o
O
10
E
150
O
'Q
O
L
1000
10tlO -
1100
11tiO
TEM P E R A T U R E (OC)
pcrnlcability vs. annealing lcmpcrature.
ults are slightly shifled for clarily.)
where d i5 grain size (I-l-m)
Correlntion Between Grnln Slze and
Mnxlmum Permeability
Thc experimcntal results presenlcd in Figures I and
3 showed a relation bctwccn grain growlh and the incrcase 01' maxill1ull1 pcrllleability.
Chikazumi
114J
showed lhat both maximulII permcability and coereive
force 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 grain
oricntalions:
0.5/J,
j of magnelic propcrties
J-Lmu
is elcpcllelcnl
00 Ule r"':":nr cootenl af lhe ingot.
es not shaw a c1ear retalion
---
(auimcnsional)
(2)
J-Lo/f ~
between
sulfur OOill:em and grain sizc, which mighl bc expectoo ir lhe laller were delermined by the volume
f raction Q~ inclusions 116 J. The occurrence or secIlization, detecleel in the samples or
Alio}' B anncaled aoove 1000° C, indicale lhal other
, ·~.r-rcrcd wilh lhe grain groWlh.
""
/f, = 1.2lf~,
A/m
(3)
where
= 41T X 10-7, H/m
lJ, = saturation inuuction. T
IJ.O
COlllbining Eqs. (2) and (3), a relation between
lIIaximum pcnneabilily anel cocrcivc force ean be found
unu cvaluulcd for a 47.5% nickcl-iron
alloy (8 J =
DISCUS-SI01\
1.55 T).
E fTecIt of Grain
Slze
011
Coerclve
FOI'ce
The experimental values of cocrcive force can be relaled [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 each
alloy. TO.e results show thal. while conslanl A depends ao lhe sulfur conlenl of lhe nlloy, lhe angular
coefficient ma)' not have thal uepenucncc. 'rhe average value af lhe five alloys is similar to the theoretical and experimental values shown in lhe lilerature
12,4J.
,;.r;-ir:-O-:J1I,
\:itJ~
,,-I
=
"'.Ia,
/f,
= 1.35 x 10-6. H (udirncnsionaJ)
'
(4)
Figure 4 shaws the experimental fit to such a linear
relalionship. The conslanls are given in Eq. (5). Its
eXlrapolulion eloes nol cross lhc origino which may
suggest that lhe irrevcrsiblc movemcnt of domuin wu11s
is nol lhe only mechanism operaling in tj1is material.
The sll1all differcnce observed belwçel1 calculaled and
ll1easured valucs of lhc slope suggcsls the applicabiJ-
J,
·Ii·'··
J-LO
0.58, 1.2
Mllteduls
Enl:lncerllll:, Vol. 11, No. I, 1989
..~
-
• 4
~.~
- -_
,.
F..J.G. Landgrat
d aJo •
AnncollnR
ond Mugndlc: f>ropcrtles or "'e-47.5%NI
-
-
2.!5
C'l.!5
T
e~ E
::t..
O I~o~
'Q
rpt~
52.. 2o
10
I
-
<>
c
~
O
6
A
O
B
<>
c
'Q
O
O
E
o
o
FtR. 4. Relalion bctween
mB..'iti mUIll
penneabllllY.
coercive
force und lhe inverse of
e
10
15
20
INVERSE OF ~GRAIN SIZE
25
(p..m-l) (10-5)
.'Ig. 6.
MUXlrllUIIl pcrlllcabilily U~ a funclion
for olloys wilh dilTcrcnl sulfur conlcnts.
ity of this relation between maximulll pcrmeability
grain size.
30
of grain size
and
1-\0;•••
I
Expcrhncntnl Rclntlol1s IJetween (;ruln Slze
and Maxlmum Permcablllty
The combination of Eq. (4) and Eq. (I) offers a relatian between maximum permeability and grain size,
as given in Eq. (6).
= --
0.68,
1-\00
(
A' + - . =p +q 3'Y IO~)
(I)d
M,
d
(6)
where d = 1.1.111.
The experimcntal results shown in Figures 5 and 6
ean be fitted to sue h a linear relalion, giving rise to
the caefficienls p and q presenled in Table 4. Once
again. the grain size dependent coeffieient shaws no
dcpcndence on sulfur content, unlike constant p. lhe
angular cocllicicnt can be used to produce experimental values of the conslant 3'V/M, (ampere):
(7)
X 10-6
(3'Y)
M, up = q' O.Gil, ILO
-
c
2
Tablc 5 shows lhe valucs for each alloy. cornparcd
to the value calculaled using B, = Ms = 1.55
and
the domain wall energy estimated by Pfeiffer et aJo
1
10
6
A
O
O
B
E
Tohle 4. Linear Regrcssion Coefficicnts
Relalion Bctwccn Grain Size and Maximum
from Eq. (6)
from lhe
Permcability
Alloy
=-
48·
.
~
imum penneabilily as u funclion
equa.l sulfur contenl (50 pplll).
~ht.B'lah Englnccrhtjl,
Voto
of grain size
A
U
U
C
D
E
0.9
0.67
0.95
_
~:t-
(, .
3.9
3.3
4.
3.6
5.l
11. No. I, 1989
----~--~_.•
~ " .•...
1.3
~\~~;
~,~-;..
~
,
to
..
,'-
,
'-.
F.J.G. Landgraf et ai.
- "
".- ~;~€'Table 5. Experimental and Theoretkal Valucs of 3-y/M.
-..
'- -:-.:-~l.~"~
<.l-f~,...
~ Anneallna and Mllgllctlc: Propertlel
of Fe-47.5
= an experimental constant for each aHoy
d = the gruin size, l1l
A"
Alio)'
2.9
2.4
3.5
2.7
3.8
3.0
0.5
2.86
The oc~urrence of lcxturc associatcd with seconuary grain growth interferes with lhe rclatian between
grain size and lllaXilllllnl pcrmeability,
fit 10 the above exprcssion.
worsening
the
REFERENCES
I.
a. CouJcrchon IIml J.F. Tícrs.
Jourt/a/ of MagnelÍ.lm
1982. vo!. 26, pp. 196-214.
F. Pfeifer Ilnd C. Radcluff. JOIlrf/al of Maglletism and
1980. vol. 19. 1'1'. 190-207.
Maglletic Mmrria/s.
W.S. Elx·r1y. Metal.f EII1(illeerinR Quarterly, 1971. vol.
11. pp. 40-47.
E. AJlcr Ilnd 11. PfcilTcr.I/EEE Tralls. Mag., 1984,
vo!. 20. pp. 1493-1495.
D.A. Colling uml R.G. AspJen. J. Appl. Phys .• 1969,
vo!. 40. 1'1'. 1571-1572.
R.T. Casanl. W.A. Klawittcr, A.A. Lykens. anJ F.W.
Ackcrl11llnn. J. App/. Phys., 1966. vaI. 37. pp. 12021204.
alld MCl811eticMateriaIs.
2.
l31. as
Eq. t6
relalio
I.
ity. The
tem
the de
work
10-' J 1m2•
The COI11(lllriSOll
sllows Ihlll
ed 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 wilh
r n (I t 2) texlurc. probably due to
the last slage aI' hot working.
e annealing tClllpcraturc prolllotes
penneability
and lawer cocrcive
~ gmin growth frolll 30 11111111900" C
50~C.
4.
5.
6.
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.,
'ent 01' the alloy makes an ill1portant
coercive force :md IlInXillllllll perwith lower sulfllr conlent rcquire
el11perature to allain the specified
ngnetic propertics.
~:t;rrimental reslIlts confinn the rclation prol. 141 bctween grain si7.e and coe rIso possible to cstnblisll a rclation
.• and maximum permeability by the
~
=-tJ.O
.68,
3.
A"+[
-
M,
d
3-y (I)J-I
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.
vI
16. 11.1'. Sluwc, ill F. Hacssller eJ. Recry.lwllizatioll
Metallic 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!. 03-
04, see. 3.
J.
MaterIais Enl:lneerlnl;.
Vol. li, No. I, 1989
• 49
Volume 8, number
MATERIALS
11.1 ~
LETTERS
November
1989
'EJ
NEW STABLE PHASE 1N THE BINARY Fe-Nd SYSTEM
3.
G. SCH:\EIDER
3.1.
Induslrial, CEMAR. Brasil
'niversidade de São Paulo, c.P. 20516, São Paulo. SP., Brasil
Ir
forn
Nd.
F.J.G. L-iL."DGRAF
11lSIIiU;O~?Pcs;;-:Jisas Tecnológicas
do Estado de São Paulo, São Paulo, SP., Brasil
\'. \'IL...~..s-BOAS, G.H. BEZERRA,
Universidade
F.P. MISSEll
de São Paulo, c.P. 20516, São Paulo. SP., Brasil
r:
f
in
anar
600
dT
the'
[ S,e-
.~::r="
tran
nea!
neal
,·r.sll!U!e, UlliversilY of DayLOn, DaYloll, OH, USA
Nd;
M
obta
',-eO 16 August 1989
tioO'
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
nrn.
H, values.
The X-ray diffraclion
pattern can be indexed using a hexagonal cell with a = 2.021 nm and c= 1.235
this,
sho\\
slow
couro
Fel7
1. 1ntroduction
2. Experimental
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].
The al!oys were prepared in the form of 2-3 g buttons by arc-melting under an Ar atmosphere. They
were then wrapped in Ta foil and sealed in Ar-filled
quartz glass capsules to be annealed at 600°C for the
times 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, 390
ppm and neodymium, 350 ppm. For the X-ray diffraction patterns, we used a Rigaku diffractometer
with 28 scanning. Magnetic measurements were performed with a vibrating sample magnetometer as described in refs. [5,6]. DT A measurements were made
with a Netzsch 404S differential thermal analyzer.
EPMA measurements were made with a lEOl 840A
eratc
rich
TI
fact
Fig.. I.
inler.-::
472
o 167-577x/89/$
(North-Holland
03.50 © EIsevier Science Publishers B.V.
Physics Publishing Division)