Hierarchical Heterogeneity in Bulk Metallic Glasses Rejuvenated by Cryogenic Thermal Cycling

The structural homogeneity of bulk metallic glasses rejuvenated by cryogenic-thermal cycling is discussed and bifurcated into two hierarchies: one can be termed as inhomogeneity with a size similar to shear transformation zones, while another is homogeneity in the magnitude of around the affected zone of nanoindentations. The hierarchical structural characteristics reflect the reduction in size, the increase in number, and the uniformity in spatial distribution, of the soft regions. The reduction in size explains the non-sacrificing or even enhanced strength, and the increased number and homogenous distribution facilitate the enhancement of plasticity for bulk metallic glasses rejuvenated using cryogenic-thermal cycling. This observed difference in homogeneity originates from the non-affine thermal strain in the intrinsically inhomogeneous bulk metallic glasses.