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Free Volume Relaxation Process in Zr50Cu40Al10 Bulk Metallic Glass Studied by Positron Annihilation Techniques

Published online by Cambridge University Press:  01 February 2011

Akito Ishii
Affiliation:
bm0801@mtr.osakafu-u.ac.jp, OSAKA PREFECTURE UNIVERSITY, MATERIAL SCIENCE ENGINEER, 1-1 NAKAKU GAKUENCHO, SAKAI, N/A, Japan
Fuminobu Hori
Affiliation:
horif@mtr.osakafu-u.ac.jp, Osaka Prefecture University, Department of Materials Science, 1-1 Gakuen-cho,Nakaku, Sakai, 599-8531, Japan
Akihiro Iwase
Affiliation:
iwase@mtr.osakafu-u.ac.jp, Osaka Prefecture University, Department of Materials Science, 1-1 Gakuen-cho,Nakaku, Sakai, 599-8531, Japan
Yoshihiko Yokoyama
Affiliation:
yy@imr.tohoku.ac.jp, Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
Toyohiko J Konno
Affiliation:
tjkonno@imr.tohoku.ac.jp, Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
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Abstract

Structural relaxation around free volume in Zr50Cu40Al10 bulk metallic glass (BMG) during isothermal annealing at 473, 573 and 673 K which are below glass transition temperature Tg =675 K have been investigated by positron annihilation lifetime (PAL) and coincidence Doppler broadening (CDB) measurements. The trends of change in positron lifetime, which correspond to the size of free volume at each annealing temperature, have a good correlation with their density change. These annealing processes obey a stretched exponential relaxation function (KWW: Kohlrausch-Williams-Watts law). Fitting parameters of KWW function, with relaxation time t0 and β, in each temperature were determined. These relaxation parameters depend on the annealing temperature, suggesting the distribution of activation energy for structural relaxation. Moreover, the profile of electron momentum distribution around free volume derived by CDB spectrum during annealing showed no appreciable change at each temperature. These facts suggest that long range chemical ordering, particularly around the free volume, dose not take place essentially.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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