Stress-strain behaviors of Ti-based bulk metallic glass and their nanostructures

We have investigated the compression stress-strain behaviors of Ti40Zr25 Cu12Ni3Be20 bulk metallic glasses prepared by Cu mold casting from various melt temperatures. Plastic strain was found to vary sensitively on the temperature of melts and subsequent annealing conditions. To understand the origin of the plasticity change, the microstructures were characterized using transmission electron microscopy and a laser-assisted three-dimensional atom probe. The fully amorphous sample cast from 1273 K showed 0.6% plastic strain, and it was enhanced to 1.3% after isothermal annealing at 573 K. The sample cast from 1423 K showed 3.0% plastic strain, from which the presence of nanocrystals with a volume fraction of about 12% was confirmed. The sample cast from a higher temperature (1573 K) contained a larger fraction of crystals, which showed limited plastic strain. The effect of the volume fraction of the nanocrystals on the plasticity of bulk metallic glasses is discussed based on the experimental results. © 2007 Materials Research Society.