Effect of Heat Treatment on the Shock Response of a Zr-Based Bulk Amorphous Alloy (BAA)

In an earlier study,\footnote{Stefan J. Turneaure, et al., Appl. Phys. Lett. \textbf{84}, 1692 (2004)} shock wave compression of a Zr-based BAA (Zr$_{56.7}$Cu$_{15.3}$Ni$_{12.5}$Nb$_{5.0}$Al$_{10.0}$Y$_{0.5})$ resulted in an elastic-plastic, strain-softening response. To understand the observed strain-softening in the as-received samples, wave profiles were obtained from samples heat treated in vacuum at three different temperatures (30 minutes at 450$^{\circ}$C, 600$^{\circ}$C and 700$^{\circ}$C). The ambient glass transition temperature is 495$^{\circ}$C. The heat treatments resulted in less than a 2{\%} increase in density and a 4-15{\%} increase in the shear sound speed while the longitudinal sound speed increases by no more than 5{\%}. For the 600$^{\circ}$C and 700$^{\circ}$C heat treatments, 50nm and $>$100nm precipitate were observed, respectively. The samples had a nominal thickness of 3mm and were shocked to a peak stress of 9.5GPa. The measured wave profiles for the as-received and the heat-treated samples show significant differences in the overall profiles and in the HEL values. These results will be presented and discussed in terms of a continuum material response. Work supported by DOE and ARL.