Loading rate effect on the creep behavior of metallic glassy films and its correlation with the shear transformation zone

The room temperature creep behaviors of metallic glassy films with a series of loading rates were systematically investigated by a spherical-tip nanoindentation. The results show that the role of loading rate on the creep deformation is material-dependent and can be intrinsically related to the shear transformation zone (STZ). Smaller STZs facilitate the more dependency of creep on the loading rate and, interestingly, a rate independency was observed in Ni-Nb, whose STZ volume is particularly larger than those in other samples. The deformation mechanism of the creep flow is discussed in the light of STZs combined with extra free volume, providing detailed explanation for the creep diversity on the loading rate in different metallic glass systems.