The Effect of Thermal Cycling Treatments on the Thermal Stability and Mechanical Properties of a Ti-Based Bulk Metallic Glass Composite

摘要

The effect of thermal cycling treatments on the thermal stability and mechanical properties of a Ti 48 Zr 20 Nb 12 Cu 5 Be 15 bulk metallic glass composite (BMGC) has been investigated. Results show that moderate thermal cycles in a temperature range of ?196 °C (cryogenic temperature, CT) to 25 °C (room temperature, RT) or annealing time at CT has not induced obvious changes of thermal stability and then it decreases slightly over critical thermal parameters. In addition, the dendritic second phases with a bcc structure are homogeneously embedded in the amorphous matrix; no visible changes are detected, which shows structural stability. Excellent mechanical properties as high as 1599 MPa yield strength and 34% plastic strain are obtained, and the yield strength and elastic modulus also increase gradually. The effect on the stability is analyzed quantitatively by crystallization kinetics and plastic-flow models, and indicates that the reduction of structural relaxation enthalpy, which is related to the degradation of spatial heterogeneity, reduces thermal stability but does not imperatively deteriorate the plasticity.