Constitutive model for high temperature deformation behavior of Ti-Zr-Ni-Be bulk metallic glass in supercooled liquid region

Abstract

A constitutive equation based on a free volume model, that describes the strain rate dependent deformation behavior of bulk metallic glasses (BMGs) within the supercooled liquid region, has been modified in this paper in order to reproduce the stress increment that occurs due to crystalline phase formation during lengthy exposure to high temperature in compression deformation. A comparison of the simulated results obtained from finite element analyzes with the compression test results for Ti-Zr-Ni-Be BMG alloy has been conducted to determine the validity of the proposed model. Plastic deformation modes such as Newtonian and non-Newtonian viscous flows of this BMG alloy were found to be reproduced well by the finite element method simulations combined with the free volume based constitutive relations and to show a phenomenon of stress increment deviated from the steady state. Therefore, the constitutive relations introduced here are expected to allow accurate reproduction of the high temperature behavior and better estimation of the formability of BMG alloys. (c) 2012 Elsevier B.V. All rights reserved.