Plastic flow and fracture of metallic glass
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c a n n i n g e l e c t r o n m i c r o s c o p e o p e r a t i n g at 25 kv in H. J. LE~MY and T. T. WANGare Members of the Technical Staff, Bell Telephone Laboratories, Inc., Murray Hill, N.J.H.S. CHEN, formerly Postdoctoral Associate, Yeshiva University,New York, N. Y., is now Staff Physicist, Allied Chemical Corp., Materials Research Center, Morristown, N. J. Manuscript submitted August 4, 1971. METALLURGICALTRANSACTIONS
the s e c o n d a r y e l e c t r o n e m i s s i o n mode. The compos i t i o n s , s t r u c t u r e s , and g l a s s t r a n s i t i o n and c r y s t a l l i z a t i o n t e m p e r a t u r e s 2 of the a l l o y s e x a m i n e d in this i n v e s t i g a t i o n a r e s u m m a r i z e d in T a b l e I. The gold and copper alloying additions shown in Table I were s e l e c t e d b e c a u s e they i n c r e a s e the stability and g l a s s t r a n s i t i o n t e m p e r a t u r e of the b i n a r y alloy, p r e s u m a b l y by i n c r e a s i n g the c o n f i g u r a t i o n a l e n t r o p y and hence the s t a b i l i t y of the liquid phase. 2 T h i s effect is e v i denced by an i n c r e a s e in the c r y s t a l l i z a t i o n t e m p e r a t u r e , T c , as shown in T a b l e I. The a m o r p h o u s - c r y s t a l l i n e t r a n s f o r m a t i o n in t h e s e alloys has been studied p r e v i o u s l y . F o r the b i n a r y a l loy, 2 c r y s t a l l i z a t i o n o c c u r s in t h r e e stages: a) h o m o geneous p r e c i p i t a t i o n of a v e r y f i n e - g r a i n e d , " m i c r o c r y s t a l l i n e " (20 to 100A) m e t a s t a b l e fcc phase within
Table I. Pd-Si Specimen Compositions, Heat Treatments, Structures, and Transformation Temperatures
No.
Composition, AtomicFractions HeatTreatment
Structure
Tg*
Tc*
362~
367~
372~
402~
373~
413~
1
Pdo.a2Sio.la
as quenched amorphous
2
Pd0.a2Sio.]s
350~ hr furnacecool
glass microcrystalline fcc + metastable
3
Pdo.s2Slo.ls
450~ hr furnacecool
fcc + metastable silicide
as quenched amorphous
sdicide
4
Pdo.79sAuo.o4Sio.16 s
5
Pdo.795Auo.o4Sio.16s 350~
6
Pdo.79sAuo.o4Sio.t6s
450~ hr. furnacecool
microcrystalline fcc + metastable sihclde
7
Pdo.7qs CUo.o6S10.16s
as quenched
amorphous
8
Pdo.77sCuo.o6 Sio.16s
350~
glass+ microcrystalhne fcc
hr.
hr
furnace cool
9
Pdo.7~sCuo.o6 Sio.]6s
450~ hr furnacecool
glass+ fcc mlcrocrystals
glass+ microcrystallinefcc + metastablesilicide
*Tg and Tc valuesfromRef. 2. Heatingrate = 20~ per rain.
VOLUME 3, MARCH 1972-699
|
o_o_ X
s
3
ca
L o. o2 , ~ u L ,
Z
gz
0)/~
O3 t~ f15
m ~ _1
N Z
+5*
o AL/L
Fig. 1--Load-elongation c u r v e s for the tensile s p e c i m e n s listed in Table I.
Table II. Mechanical Properties of PdSi Alloys
Num- DPH, ber kg/mm2 1 2 3
118 116 232
4 5 6
127 91 161
7 8 9
129 113 141
E, dyne/cm2
YS, dyne/era 2
UTS, dyne/cm2
TS
6.8 X 10n 8.25 X 1 0 9 2.7 • 101~ 0.0025 7.5X 10n 1.35Xl0 l~ 2.75X 10l~ 0.004 Specimensextremely 0 brittle no tensde data 8.5 X lOl* 9.5 X 109 2.7 X 10l~ 0.003 10X 10n
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