High strain rate sensitivity of hardness in Ti-Zr-Hf-Be-(Cu/Ni) high entropy bulk metallic glasses

Nanoindentation tests on the Ti20Zr20Hf20Be20(Cu20-xNix) (x = 0, 12.5, 20 at.%) high entropy bulk metallic glasses (HE-BMGs) indicate both their average hardness and moduli show a significant loading strain rate-dependent behaviour. In special, the strain rate sensitivity of hardness measured for the prepared TiZrHfBeNi HE-BMG is up to 0.056 which is the highest value reported for BMGs so far. Such high strain rate sensitivity of hardness is likely due to the high-entropy effect, which makes the amorphous structure more homogeneous. In addition, the high entropy coupled with amorphous structure manifests as small shear transformation zone (STZ) volumes that could make the shear bands hard to be initiated.