Severe Plastic Deformation of Amorphous Alloys

Abstract

Bulk metallic glasses having a disordered amorphous structure have been in the focus of recent intensive materials research due to their special mechanical properties, however, these materials exhibit brittleness in conventional unconstrained deformation modes. High-pressure torsion as a special severe plastic deformation method, which applies constraints on the material, can induce significant plasticity in metallic glasses. Apart, the deformation can promote structural changes in the glass, such as anisotropy and nanocrystallization. The inhomogeneity generated by torsional shear deformation in bulk metallic glasses can be detected in internal surfaces. The final structure and morphology of the deformed material depend on the processing parameters (deformation rate, shear strain, temperature and pressure) of the high-pressure torsion apparatus.

Severe plastic deformation of bulk metallic glasses by high pressure torsion results in a dense and complex shear band structure (a, b). On contrary, glassy samples exhibit well-separated parallel shear bands developed after torsion at ambient pressure with the same shear strain (c). The complex shear band structure can form only at much higher ultimate strains at low pressure (d).