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YOUNG’S MODULUS OF Fe-Mn
E. Török, M. Weller, G. Hausch
To cite this version:
E. Török, M. Weller, G. Hausch. YOUNG’S MODULUS OF Fe-Mn. Journal de Physique Colloques,
1983, 44 (C9), pp.C9-477-C9-480. �10.1051/jphyscol:1983969�. �jpa-00223419�
JOURNAL DE PHYSIQUE
Colloque C9, suppl6ment au n012, Tome 44, d6cembre 1983 page C9-477
YOUNG'S MODULUS OF Fe-Mn
E. TBrijk, M. wellerr and G. Hauschr*
Institut Dr. Strawnann AG, CH-4437 WaZdenburg, SwitzerZand r ~ a c c - ~ ~ a n c k - ~ n s t i t u t far MetaZ Zfo~sckung, Institut far Werkstoffwissensckaften, 0-7000 Stuttgart, F.R.G.
**
VacuwnschmeZze GmbH, 0-6450 H a m u I, F.R.G.RBsumB
-
Le module de Young et le frottement intsrieurd'alliages Fel-xMnx (0,l
2
x2
0,9) ont 6t& mesurBs en fonction de la temperature. Une anomalie en forme de marche se produit d T ; elle est d'autant plus forte que les alliages sont plus ricEes en fer. An-dessous de TN apparait une reduction de dE/dT. Pour les alliages avec x = 0,9 un pic de frottement intsrieur est observe d TN et aux alentours de-
25 OC. Le dernier pic est attribug d un mouvement des parois de domaines antiferromagnetiques induit par la contrainte.Abstract
-
Young's modulus of Fel-xMnx alloys with 0.1 (x ( 0.9 has been measured as a function of temperature. A step type anomaly occurs at T which is largest for Fe-rich alloys and a reduction in dE/dT gelow T.
For the alloy with x = 0.9 a high internal friction peak is Yound at T and at Y -25 OC. TheN .
latter peak is attributed to a stress lnduced movement of domain boundaries.
Introduction
-
y-Fe Mn alloys are known to order antiferromagnet- ically at low tempe$a?urgs. The magnetic phase diagram of these alloys is well established [I-
41. Endoh and Ishikawa [I] investigated alloys covering the whole concentration range. They used small amounts of carbon or copper to stabilize the y-phase at the Fe-rich and Mn- rich side, respectively. 3 types of maqnetic structure are found:i) a colinear spin structure typical of y-Fe on the Fe-rich side ii) a noncolinearspin structure for 0.2 ( x ( 0.6
iii) a noncolinear spin-structure typical of y-Mn on the Mn-rich side.
For alloys with
x
< 0.5 no deviation from cubic symmetry has been found below the Nee1 temperature TN Fa] while for the Mn-rich alloys a tetragonal or orthorhombic distortion occurs [5].Measurements of Young's modulus of Fe-Mn and Fe-Mn based alloys have been reported [3, 6
-
81. Both Young's and shear modulus show step type anomalies at TN. Russian workers [2, 31 reported, in addition, an antiferromagnetic antiferromagnetic transition at -100 OCwhose nature, however, was not further specified.
Experimental
-
7 alloys have been prepared whose compositions are listed in table 1. We have used, similar to Endoh et a1 Ill, small amounts of carbon and copper to stabilize the fcc structure. The Mn-rich alloys have been annealed at 1150 OC for 15 min. and then quenched into water. The other alloys were quenched from 1000 OC.From metallographic inspection all alloys were single phase except alloy No 7 where signs of a fcc ~ f c t transformation could be de- tected.
Young's modulus and the internal friction were determined by the resonant bar technique [9] using specimens with dimensions
50 x 5 x 1 mm3. The Ngel temperatures were determined from the peak Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983969
JOURNAL DE PHYSIQUE
Fig. 1
-
Young's modulus, E, of FelVxMnx alloys (0.1 (x-6
0.9).The lnternal friction,Q
,
of the alloy with X = 0.9 is included in the figure. The composition of alloys No 1-
7 are listed in table 1.temperatures measured by dif- ferential scanning calorimetry
(DSC)
.
Results and Discussion
-
Thetemperature dependence of Young's modulus, E, ~ n d of the internal friction, Q-
,
are presented in b Fig. 1 and 2, respectively.All alloys exhibit a step type anomaly which is associated with antif erromagnetic ordering. The temperature of the anomalous decrease of E approximately co- incides with the N6el tempera- tures listed in table 1 which
TEMPERATURE ( O C ) have been measured by DSC.
For Fe-rich alloys the magnitude of the anomaly continuously in- creases with increasing Fe-con- tent which agrees very well with previous data. For alloys around Fe Mn the anomaly has nearly disappeared which agrees with previous da52
[ g ? .
Russian workers [2, 31 reported a low temperature transfor- mation at -100 OC; our data give no evidence for such a transfor- mation. If one compares the temperature coefficient, dE/dT, above and below TN it can be easily seen that antiferromagnetic ordering leads to a less negative value for dE/dT, i. e., these alloys are similar to the well known Fe-Ni invar alloys except for the step type anomaly which do not occur for the latter alloys [lo]. Compared to Fe-Ni alloys, the antiferromagnetic AE-effect in Fe-Mn alloys is too small to fully compensate for the normal temperature variation so that these alloys have not found a large scale technical application as constant modulus alloys 181.Endoh et a1 [Ill have determined
c'=
(CI1-C 2)/2for a Fe OMn30 single crystal by neutron diffraction. Their data Suggest a cloze correspond- ence to Fe-Ni invar alloys. However, between 300 and 500 K only 3 data points are given so that from their data no decision can be made whether C' varies continuously or not across TN.Lenkkeri [ 1 2 ] , on the other hand, has studied a Fe-38.5 at.% Mn alloy by ultrasonics. His data show that C 1 , in fact, does vary discontinu- ously across TN. For this particular alloy C r dropped by about 8 %
below T
,
while the other elastic constants, C and C were less affecteg. Our results (Fig. 1) indicate that tke anomifAus elastic behavior of C r and Cg4 must be even larger for alloys having larger Fe concentrations. A simple calculation shows that the anomaly for alloys No 1 and 2 is so large that it cannot be explained by an anomalous behavior of C r alone but Cg4 must also exhibit a large drop below TN.F i q . 2
-
I n t e r n a l f r i c t i o n , Q-,
of Fed-xMnx a l l o y s . The c o m p o s i t i o s o f a l l o y s No 1 , 3 and 4 a r e l i s t e d i n t a b l e 1The p h y s i c a l o r i g i n o f t h e d i s c o n t i n u o u s b e h a v i o r o f t h e e l a s t i c c o n s t a n t s a t TN and t h e p e c u l i a r c o n c e n t r a - t i o n dependence a s d i s c u s s e d above i s n o t c l e a r . The ab- s e n c e of any l a t t i c e d i s t o r - t i o n [I 11 ( t e t r a g o n a l o r rhombohedral) p o i n t s t o a
0
1
I I II
l a r g e band s t r u c t u r e con--100 0 100 200 t r i b u t i o n which i s d i f f i c u l t TEMPERATURE i°C) t o a s s e s s r i g o r o u s l y [ 131
.
The change i n dE/dT below TN, however, may b e explained I n t e r m s o f a n exchange con- t r i b u t i o n t o t h e e l a s t i c c o n s t a n t s i n t h e same way a s g i v e n p r e v i o u s - l y f o r t h e f e r r o m a g n e t i c Fe-Ni and Fe-Pt a l l o y s [ I 4
-
161.When going t o t h e Mn-rich s i d e t h e r e i s a l a r g e d e c r e a s e i n E a s shown i n F i g . 1. Low e l a s t i c moduli a r e c h a r a c t e r i s t i c o f Mn-based a l l o y s . T h i s f e a t u r e may be r e l a t e d t o t h e r e d u c t i o n i n c o h e s i v e e n e r g y o b s e r v e d f o r 3 d t r a n s i t i o n m e t a l s due t o t h e e f f e c t o f e l e c - t r o n i n t e r a c t i o n s which h a s been shown t o b e l a r g e s t f o r a h a l f - f i l l e d 3 d band [ 1 7 ] .
A l l o y No 7 , b e i n g r i c h e s t i n Mn-concentration, behaves most anomalous i n t h a t Young's modulus s t r o n g l y d e c r e a s e s on c o o l i n g f o r T
5
50 OC.T h i s e f f e c t , however, i s p r o b a b l y n o t a n i n t r i n s i c e f f e c t , b e c a u s e
-
f o r Mn-rich a l l o y s
-
a t e t r a g o n a l o r orthorhombic d i s t o r t i o n o f t h e l a t t i c e o c c u r s [ 5 ] . I n o r d e r t o minimize t h e e l a s t i c e n e r g y i n t e r n a l domains may b e formed a t TN o r a t some t e m p e r a t u r e TD < TN [ I 81 which can g i v e r i s e t o domain boundary e f f e c t s t h u s l o w e r i n g t h e e l a s t i c modulus and c r e a s i n g t h e - n t e r n a l f r i c t i o n . The l a r g e i n t e r n a l f r i e t i o n peak ( Q 'max = 2 x 10 ') o b s e r v e d f o r t h i s a l l o y (No 7 ) a t a b o u t -25 OC i s a t t r i b u t e d t o t h i s mec anism. T h i s a l l o y a l s o e x h i b i t s a- 9
l a r g e i n t e r n a l f r i c t i o n peak, Q max = 2.5 x 10-3, a t TN.
The i n t e r n a l f r i c t i o n o f a l l o t h e r a l l o y s s t u d i e d i s r a t h e r s m a l l a s s h wn i n f i g . 2. T9ey e x h i b i t a s m a l l i n t e r n a l f r i c t i o n peak,
-9
Q max < 1.5 x 10
,
a t TN.T a b l e 1
-
Chemical c o m p o s i t i o n ( w t . % ) and Ngel t e m p e r a t u r e T NNo A l l o y Fe Mn C Cu
--
I 'Fe90Mnl ' 0 . 9 ~ ~ 0 . 0 4 b a l 9.2 0.9
-
N.D.2 IFe ~ 2 2 ' 0 . 9 6 0.04 b a l 21.5 0.9
-
N.D.3 ~ e - 2 8 ~ n b a l 29.0
- -
41 04 Fe-33.5Mn b a l 33.5
- -
4305 Fe- 4 2Mn b a l 42.2
- -
4756 (Fe15Mn85)0. 95CU0 .05 b a l 79.9
-
5.7 4357 ( F e ? ~ M n 9 0 ) 0 . 9 ~ ~ ~ 0 . 0 5 b a l 84.7
-
5.7 440J O U R N A L DE PHYSIQUE
References
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Vaganova, L.A. and Belenkova, M.M.; fiz. metal. metalloved.
47 (1 9 7 9 ) 1 8 0
[ 51 Demin, S.A.; Ustinov, A.I. and Chnistovr fiz. metal.
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1121 Lenkkeri, J . T . ; J . Phys. F 11 ( 1 9 8 1 ) 1991 1131 Steinemann, S.; JMMM 1 2 ( 1 9 7 9 ) 1 9 1
[ I 4 1 Hausch, G.; J . Phys. Sec. Japan 37 ( 1 9 7 4 ) 8 1 9 [ I 5 1 Wohlfarth, E.P.; J. Phys. F 6 ( 1 9 7 6 ) L 59 [ I 6 1 Hausch, G.; J. Phys. F 7 ( 1 9 7 7 ) L 127
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