Crystallization and hardening of Zr-40 at.% Cu thin film metallic glass: Effects of isothermal annealing

Effects of isothermal annealing on structural relaxation, crystallization and mechanical behavior of Zr-40 at.% Cu thin film metallic glass (TFMG) are reported. Two annealing temperatures have been chosen in the supercooled liquid region (AT) and one below the glass transition temperature (T-g). During annealing the free volume decreased and nanocrystals nucleated into the matrix. Results show that the nanocrystalline CuZr2 intermetallic phase precipitates in the glassy matrix with respect to the annealing temperature and duration. When annealed below Tg, the structural relaxation induces a slight improvement of the mechanical properties with a hardness and Young's modulus variation of about 2.5% and 9.0% compared with the as-deposited values. At higher temperatures, it is shown that hardness increases of about 5.5% and 25.0% after a heat treatment of 60 min at 350 C and 380 degrees C, respectively. The elastic modulus follows a time dependent increase from -100 GPa (as-deposited) up to -105 GPa after a one-hour annealing at 350 degrees C and -125 GPa at 380 degrees C, respectively. (C) 2015 Elsevier Ltd. All rights reserved.