THERMOMECHANICAL CHARACTERIZATION OF CU47.5ZR47.5AL5 BULK METALLIC GLASS WITHIN THE HOMOGENEOUS FLOW REGIME

Abstract

We present a systematic study of the high temperature deformation behavior of a Cu47.5Zr47.5Al5 ternary bulk metallic glass over a wide range of strain rates within the homogeneous flow regime. The apparent viscosity and the effective strain rate determined by thermomechanical analysis in the low stress regime strongly depend on the isothermal annealing temperature and the applied compressive force. Three distinct flow modes, viz. inhomogeneous, non-Newtonian and Newtonian flow, can be distinguished from compression tests, The strain rate-stress data, deduced from both thermomechanical analysis and quasi-static compression tests, were used to construct a Norton-type plot indicating a transition from Newtonian to non-Newtonian flow. The significance of these findings for the expected macroscopic shaping capability based on the dynamic materials model as well as the change of the amount of atomic-scale flow defects such as free volume is also investigated. (C) 2008 Elsevier Ltd. All rights reserved.