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Dilatometric investigation of AS-quenched Fe82B18 and Cu60Zr40 samples under tensile stress
Scripta METALLURGICA
Vol. 16, pp. 693-696, 1982 Printed in the U.S.A.
Pergamon Press Ltd. All rights reserved
DILATOMETRIC INVESTIGATION OF AS-QUENCHED Fe82BI8 AND Cu60Zr40 SAMPLES UNDER TENSILE STRESS
E.Girt~ P . T o m i 6 : T . M i h a 6 + and A.Kur~umovi6* +-Faculty of Sciences,Unlversity of Sarajevo,Yugoslavia *-Institute of Physlcs,University of Sara3evo,Yugoslavia (Received February 17, 1982) (Revised March 29, 1982) Introduction Tensile stress has a significant influence on the low-temperature relaxation processes of as-quenched samples of metallic glasses(1).We have used a dilatometric method to study the kinetics of the low-temperature relaxation of as-quenched samples under tensile stress.The samples we used were a metallic-metalloid system FeR~BIR and a metallic-metallic system Cu~nZr~n. In both systems we observed a t r a ~ i £ [ o n to a more stable,relaxed p h a s e . D ~ r i ~ this transition a contraction of the sample occurred,i.e, the as-quenched samples lost some of their free volume excess.The contraction d u r i n g low-temperature relaxation can be quantitatively described by annihilation of low and high density regions (2). The loss of the excess free volume directly contributes to the relaxation and the result of that fact can be described by logarithmic kinetics (3).It is possible to identify the process which is driven by the loss of free volume during the low-temperature relaxation.The possibility of identifying a particular process would give us important information about structural changes in the observed systems.That is the intention of this paper. Experiment We used a home-made dilatometer described earlier (4) to measure the change in length of as-quenched amorphous Fe89B, R and Cu60Zr~n samples as a function of time under tensile stress at room ~ e ~ e r a t u r e . Th~Vsamples in the form of thin ribbons about 18 mm long were obtained by a rotating wheel technique.The FeR~BIR samples were 2.016 m m wide and 0.032 ram thick, and the width and thickness ~f the Cu60ZrAn samples was 0.2004 nun and 0.030 ram, respectively. The FeR~B18 saddles were subjected to a force of 0.16 N, 0.36 N and 0.56 N, which induc~a ~ tensile stress of 2540 kPa, 5540 kPa and 8540 kPa, respectlvely.The same force was induced on the CufioZr40 samples at a tensile stress of 2970 kPa, 5970 kPa and 8970 kPa, respectlvely.The output of the dilatometer was simultaneously recorded on a Xy recorder and read off on a digital voltmeter every 30 sec. Results The changes in length of the Fe B samples as a function of time are shown in Fig.la, Fig.2a and Fig.3a.The a p ~ i ~ tensile stresses were 2540 kPa, 5540 kPa and 8540 kPa, respectively.The same dependences for the CUKnZr4n samples with applied stresses of 2970 kPa, 5970 kPa and 8970 kPa were shown ~n Fig.lb,Fig.2b and Fig.3b. The time dependence obtained for the same sample under different stresses are very similar, but they are very different for the two different samples.As described in (3), the results were fitted to the equation:
~) =
Blnt + A ,
where A and B are constants. In each figure the fits to the above equation are represented by full points and the experimental results by empty circles.For both materials a part of the process follows a logarithmic dependence.
693 0036-9748/82/060693-04503.00/0 C o p y r i g h t (c) 1982 Pergamon P r e s s Ltd.
694
0~ Lo
DILATOMETRIC INVESTIGATION OF METALLIC GLASSES
-0,1
6:25&OkPo
°:oO
%0 %o os o
-0,2
No.
6
C%0Zr40
FeeaB~t
%
16,
%
0,0
%
Vol.
G:29?OkPo
eo
8
-0.~
o ° e
~°ql° a • ° ° ° ° ° ° O o ooooOOOooooo - • OOoooooooo oo
Oo8O 0|#°$,
-0.3
e
°:-0:.
"0::.:
Fig.l a.The length change dependence of Fe82B18sample under tensile stress of 2540kPa. b.The length change dependence of Cu~nZ94n under tensile stress of 2970 kPa. The experimental results are represe~£ed 5y empty circles and the fits to the given equation by full points•
0~
xld
- 0,1
|
o
0~
FeB2 8~8 G : 5540 kPo
:
(u6o Zr~o
•o
%
- 0,1
G • 5970 kPa g o
-OJ
•
J8 e
- 02
o
eollo0o~,8 • o 4) o o • o o o o o o • o o • • • o
lc~)0
•
° ° ° °'° ° °"° "b *'* %° %°" I ° " ° * o ° °,0 •
-03
~0
• o
.s)
S()O
10'00
t(s)
Fig.2 a.The length change dependence of Fe82B18under tensile stress of 5540 kPa. b.The length change dependence of Cu.^Zr4^under tensile stress of 5970 kPa.The full points represent the fits and t ~ experimental results are given by empty circles•
0~. o
0,0 FeE2 B1g &=eS4OkPa
%
- 0.2
• 0,1
-0~ *8
8oe o ~
0
0 0
o
G:89?OkPo
g
a a oa aaa~n
o
"8 e$o
"0,~
Cu~Zr~
o IJ°
$ OO8o
aaaan= S88g°ooooooo
.
a maa
naaa a
ooooooO°
oaoooOO°
-02 0 0 @ 0 @ @0 0 0 0 Q 0 0 0
o o
eeeeeeeete•eeee•ee•eee
sb0
,~
eel
.-)
Fig.3 a.The length change dependence of FeR~B.^under tensile stress of 8540 kPa b.The length change dependence of Cu.^Z~.^under tensile stress of 8970 kPa The 4u squares represent the values of ( i/~Yflowdeterminated from the equation.
Vol.
16, No. 6
DILATOMETRIC
INVESTIGATION OF METALLIC GLASSES
695
The parameters which define this dependence are given in Table I: TABLE I The parameter which define the time dependence of the length change: A are constants, r- is the variance of I. The sample
Tensile stress (kPa)
A
B
and B
r2
Fe82BI8
2540 5540 8540
207.54 201.30 300.42
-20.04 -19.12 -39.04
0.94 0.80 0.96
CQ60Zr40
2970 5970 8970
138.55 180.23 155.82
-13.46 -23.85 -28.56
0.98 0.96 0.99
The Fe82BI8 samples relaxed in the same manner, i.e. independently of the tensile stress.ln the first phase the relative length change for this system can be described as: 41 --[ = B int + A, where A and B are constants. In the second phase there is no longer a change in the length, apparently the system is in a state where there is no further loss in free volume. The CU~nZr4n system relaxes in two ways.For lower applied stresses the length change folI~ws £he above dependence (Fig. lb and Fig.2b) over the entire measured range.For the highest stress (8970 kPa), there is initially a contraction described by the logarithmic law, but subsequently the sample expands (Fig.3b). The behaviour of the sample shown in Fig.3b is a consequence of the creep process which cannot be neglected for higher values of tensile stress.We can analyse the results in terms of the relation A1 =(_ ~I ) + (~--r) (-~) ex -~ in ~ flow
' where: ( ~ i / i ) v are experimental values of the relative length change, ( ~ 1 / i ) e~ ~ relative contraction due to loss of excess free volume , (~I/i)~? relative length increase caused by creep. Experim~lly (-AI/I)I n is independent of Stress, thus we can determine the time dependence of (AI/IT_ 1 . If we take for (~I/i)~ n the fitted values obtained for initial behaviour o~ ~ g . 3 b , the upper relatio~ enables the evaluation of (~i/i)-- O (for the known experimental data).Those values of (~i/i) .... are shown ~ ~quares in Fig. 3b. It can be seen that the contribution of ~ p to the length change has a linear dependence. For the both systems, FeRgB,. and Cu~nZr40 , there are small periodic oscillations in ~i/l,especially d ~ i ~ 8 long t ~ t s , whose origin is presently not understood. In the Cu~0ZrAn system they are always present, whereas in Fe82BI8 they appear only in th~ ph~§e where ~ i / i is stable. Discussion The results show that the relaxation of Fe82B,~ and Cu,^Zr4^ metallic glasses under tensile stress is ruled by different p r 6 8 e s s e s . T ~ relaxation of Fes-B.^ has two phases. In the first one, the atom migration is allowed because of ~ h ~ f r e e volume excess.The migration process enables formation of very stable clusters with Fe~B as a base (4,5).The formation of these stable configurations stops the proces~ of volume change and the logarithmic kinetic law is no longer followed. The model of Mirogushi et al (6) explains the relaxation of the Cu6nZr4n system.There are no clusters which might stop the migration so the leng£h ~ a n g e always has a logarithmic loss of free volume.At higher tensile stresses and longer duration this is partially obscured by the occurrance of creep. It can
696
DILATOMETRIC
INVESTIGATION OF METALLIC GLASSES
Vol.
16, No. 6
be seen that creep is linear with time. Acknowled@ements The authors wish to thank the Scientific Fund of SRBiH for the financial support of the work.Thanks also to Dr J.Cooper for his final revision of the paper. References (1) (2) (3) (4) (5) (6)
E.Girt,P.Tomi6,T.Miha6 and A.Kur~umovi6, Proc.of the IV Int.Conference on Rapidly Quenched Metals,Sendai, august 1981. T.Egami,K.Maeda and V.Vitek, Phil.Mag.41A,883 (1980). E?Girt,A.Kur~umovi6 and T.Miha6,J.Phys. E.Sci. Inst. 13,898,(1980). M.Kashimura and M.Takahashi,Proc.of the IV Int.Conference on Rapidly Quenched Metals, Sendal, 1981. I.Maewska,B.J.Thijsse and M.Radelaas, Proc.Of the IV Int.Conference on Rapidly Quenched Metals, Sendal 1981. T.Mirogushi,T.Kude,T.Irisava,N.Watanabe,N.Niimura,M.Nisawa and K.Suzuki, Proc.of the III Int.Conference on Rapidly Quenched Metals,Vol.2,384(1978).
Vol. 16, pp. 693-696, 1982 Printed in the U.S.A.
Pergamon Press Ltd. All rights reserved
DILATOMETRIC INVESTIGATION OF AS-QUENCHED Fe82BI8 AND Cu60Zr40 SAMPLES UNDER TENSILE STRESS
E.Girt~ P . T o m i 6 : T . M i h a 6 + and A.Kur~umovi6* +-Faculty of Sciences,Unlversity of Sarajevo,Yugoslavia *-Institute of Physlcs,University of Sara3evo,Yugoslavia (Received February 17, 1982) (Revised March 29, 1982) Introduction Tensile stress has a significant influence on the low-temperature relaxation processes of as-quenched samples of metallic glasses(1).We have used a dilatometric method to study the kinetics of the low-temperature relaxation of as-quenched samples under tensile stress.The samples we used were a metallic-metalloid system FeR~BIR and a metallic-metallic system Cu~nZr~n. In both systems we observed a t r a ~ i £ [ o n to a more stable,relaxed p h a s e . D ~ r i ~ this transition a contraction of the sample occurred,i.e, the as-quenched samples lost some of their free volume excess.The contraction d u r i n g low-temperature relaxation can be quantitatively described by annihilation of low and high density regions (2). The loss of the excess free volume directly contributes to the relaxation and the result of that fact can be described by logarithmic kinetics (3).It is possible to identify the process which is driven by the loss of free volume during the low-temperature relaxation.The possibility of identifying a particular process would give us important information about structural changes in the observed systems.That is the intention of this paper. Experiment We used a home-made dilatometer described earlier (4) to measure the change in length of as-quenched amorphous Fe89B, R and Cu60Zr~n samples as a function of time under tensile stress at room ~ e ~ e r a t u r e . Th~Vsamples in the form of thin ribbons about 18 mm long were obtained by a rotating wheel technique.The FeR~BIR samples were 2.016 m m wide and 0.032 ram thick, and the width and thickness ~f the Cu60ZrAn samples was 0.2004 nun and 0.030 ram, respectively. The FeR~B18 saddles were subjected to a force of 0.16 N, 0.36 N and 0.56 N, which induc~a ~ tensile stress of 2540 kPa, 5540 kPa and 8540 kPa, respectlvely.The same force was induced on the CufioZr40 samples at a tensile stress of 2970 kPa, 5970 kPa and 8970 kPa, respectlvely.The output of the dilatometer was simultaneously recorded on a Xy recorder and read off on a digital voltmeter every 30 sec. Results The changes in length of the Fe B samples as a function of time are shown in Fig.la, Fig.2a and Fig.3a.The a p ~ i ~ tensile stresses were 2540 kPa, 5540 kPa and 8540 kPa, respectively.The same dependences for the CUKnZr4n samples with applied stresses of 2970 kPa, 5970 kPa and 8970 kPa were shown ~n Fig.lb,Fig.2b and Fig.3b. The time dependence obtained for the same sample under different stresses are very similar, but they are very different for the two different samples.As described in (3), the results were fitted to the equation:
~) =
Blnt + A ,
where A and B are constants. In each figure the fits to the above equation are represented by full points and the experimental results by empty circles.For both materials a part of the process follows a logarithmic dependence.
693 0036-9748/82/060693-04503.00/0 C o p y r i g h t (c) 1982 Pergamon P r e s s Ltd.
694
0~ Lo
DILATOMETRIC INVESTIGATION OF METALLIC GLASSES
-0,1
6:25&OkPo
°:oO
%0 %o os o
-0,2
No.
6
C%0Zr40
FeeaB~t
%
16,
%
0,0
%
Vol.
G:29?OkPo
eo
8
-0.~
o ° e
~°ql° a • ° ° ° ° ° ° O o ooooOOOooooo - • OOoooooooo oo
Oo8O 0|#°$,
-0.3
e
°:-0:.
"0::.:
Fig.l a.The length change dependence of Fe82B18sample under tensile stress of 2540kPa. b.The length change dependence of Cu~nZ94n under tensile stress of 2970 kPa. The experimental results are represe~£ed 5y empty circles and the fits to the given equation by full points•
0~
xld
- 0,1
|
o
0~
FeB2 8~8 G : 5540 kPo
:
(u6o Zr~o
•o
%
- 0,1
G • 5970 kPa g o
-OJ
•
J8 e
- 02
o
eollo0o~,8 • o 4) o o • o o o o o o • o o • • • o
lc~)0
•
° ° ° °'° ° °"° "b *'* %° %°" I ° " ° * o ° °,0 •
-03
~0
• o
.s)
S()O
10'00
t(s)
Fig.2 a.The length change dependence of Fe82B18under tensile stress of 5540 kPa. b.The length change dependence of Cu.^Zr4^under tensile stress of 5970 kPa.The full points represent the fits and t ~ experimental results are given by empty circles•
0~. o
0,0 FeE2 B1g &=eS4OkPa
%
- 0.2
• 0,1
-0~ *8
8oe o ~
0
0 0
o
G:89?OkPo
g
a a oa aaa~n
o
"8 e$o
"0,~
Cu~Zr~
o IJ°
$ OO8o
aaaan= S88g°ooooooo
.
a maa
naaa a
ooooooO°
oaoooOO°
-02 0 0 @ 0 @ @0 0 0 0 Q 0 0 0
o o
eeeeeeeete•eeee•ee•eee
sb0
,~
eel
.-)
Fig.3 a.The length change dependence of FeR~B.^under tensile stress of 8540 kPa b.The length change dependence of Cu.^Z~.^under tensile stress of 8970 kPa The 4u squares represent the values of ( i/~Yflowdeterminated from the equation.
Vol.
16, No. 6
DILATOMETRIC
INVESTIGATION OF METALLIC GLASSES
695
The parameters which define this dependence are given in Table I: TABLE I The parameter which define the time dependence of the length change: A are constants, r- is the variance of I. The sample
Tensile stress (kPa)
A
B
and B
r2
Fe82BI8
2540 5540 8540
207.54 201.30 300.42
-20.04 -19.12 -39.04
0.94 0.80 0.96
CQ60Zr40
2970 5970 8970
138.55 180.23 155.82
-13.46 -23.85 -28.56
0.98 0.96 0.99
The Fe82BI8 samples relaxed in the same manner, i.e. independently of the tensile stress.ln the first phase the relative length change for this system can be described as: 41 --[ = B int + A, where A and B are constants. In the second phase there is no longer a change in the length, apparently the system is in a state where there is no further loss in free volume. The CU~nZr4n system relaxes in two ways.For lower applied stresses the length change folI~ws £he above dependence (Fig. lb and Fig.2b) over the entire measured range.For the highest stress (8970 kPa), there is initially a contraction described by the logarithmic law, but subsequently the sample expands (Fig.3b). The behaviour of the sample shown in Fig.3b is a consequence of the creep process which cannot be neglected for higher values of tensile stress.We can analyse the results in terms of the relation A1 =(_ ~I ) + (~--r) (-~) ex -~ in ~ flow
' where: ( ~ i / i ) v are experimental values of the relative length change, ( ~ 1 / i ) e~ ~ relative contraction due to loss of excess free volume , (~I/i)~? relative length increase caused by creep. Experim~lly (-AI/I)I n is independent of Stress, thus we can determine the time dependence of (AI/IT_ 1 . If we take for (~I/i)~ n the fitted values obtained for initial behaviour o~ ~ g . 3 b , the upper relatio~ enables the evaluation of (~i/i)-- O (for the known experimental data).Those values of (~i/i) .... are shown ~ ~quares in Fig. 3b. It can be seen that the contribution of ~ p to the length change has a linear dependence. For the both systems, FeRgB,. and Cu~nZr40 , there are small periodic oscillations in ~i/l,especially d ~ i ~ 8 long t ~ t s , whose origin is presently not understood. In the Cu~0ZrAn system they are always present, whereas in Fe82BI8 they appear only in th~ ph~§e where ~ i / i is stable. Discussion The results show that the relaxation of Fe82B,~ and Cu,^Zr4^ metallic glasses under tensile stress is ruled by different p r 6 8 e s s e s . T ~ relaxation of Fes-B.^ has two phases. In the first one, the atom migration is allowed because of ~ h ~ f r e e volume excess.The migration process enables formation of very stable clusters with Fe~B as a base (4,5).The formation of these stable configurations stops the proces~ of volume change and the logarithmic kinetic law is no longer followed. The model of Mirogushi et al (6) explains the relaxation of the Cu6nZr4n system.There are no clusters which might stop the migration so the leng£h ~ a n g e always has a logarithmic loss of free volume.At higher tensile stresses and longer duration this is partially obscured by the occurrance of creep. It can
696
DILATOMETRIC
INVESTIGATION OF METALLIC GLASSES
Vol.
16, No. 6
be seen that creep is linear with time. Acknowled@ements The authors wish to thank the Scientific Fund of SRBiH for the financial support of the work.Thanks also to Dr J.Cooper for his final revision of the paper. References (1) (2) (3) (4) (5) (6)
E.Girt,P.Tomi6,T.Miha6 and A.Kur~umovi6, Proc.of the IV Int.Conference on Rapidly Quenched Metals,Sendai, august 1981. T.Egami,K.Maeda and V.Vitek, Phil.Mag.41A,883 (1980). E?Girt,A.Kur~umovi6 and T.Miha6,J.Phys. E.Sci. Inst. 13,898,(1980). M.Kashimura and M.Takahashi,Proc.of the IV Int.Conference on Rapidly Quenched Metals, Sendal, 1981. I.Maewska,B.J.Thijsse and M.Radelaas, Proc.Of the IV Int.Conference on Rapidly Quenched Metals, Sendal 1981. T.Mirogushi,T.Kude,T.Irisava,N.Watanabe,N.Niimura,M.Nisawa and K.Suzuki, Proc.of the III Int.Conference on Rapidly Quenched Metals,Vol.2,384(1978).