Structural relaxation and shear softening of Pd- and Zr-based bulk metallic glasses near the glass transition

Precision measurements of the high-frequency shear modulus G and internal friction Q-1 on bulk Pd- and Zr-based glasses upon thermocycling from room temperature up to the glass transition and back have been performed. Together with the pronounced shear softening and related increase of the internal friction upon approaching the glass transition temperature, a strong hysteresis of G and Q-1 upon cooling has been found. It has been revealed that the shear softening can be quantitatively described as a result of the generation of interstitialcy defects near the glass transition.