Plasticity Driven by Amorphous Shear Band: Role of Heterogeneity

The occurrence of amorphous shear bands in crystalline materials usually leads to brittle fracture. However, in some materials it was found to have the opposite effect, acting as a driver of plasticity. Recent research has found that this kind of shear-band plasticity should follow certain necessary conditions such as small density change (<6%) during amorphization and lower energy for shear-band formation than cleavage. This work demonstrates in an intermetallic that the shear-band plasticity can be greatly enhanced by introducing atomic-scale structural heterogeneity. The samples with such heterogeneity can be plastically deformed above a compressive engineering strain of about 5%, while the samples without the heterogeneity do not show significant plasticity even though the strain reaches 10%. Atomistic analysis reveals that the existence of soft and hard spots induces progressive formation and delocalization, rather than abrupt shear localization, of shear bands. This finding provides a potential solution to future application of such plasticity mechanism in developing new materials with high toughness.