Micromechanical mechanism of yielding in dual nano-phase metallic glass

Through detailed experimental and theoretical analyses, here we uncover the mechanism of plasticity initiation in the Ni-P nano-grained metallic glass (NGMG) which contains nano-sized hard amorphous inclusions and soft amorphous inter-granular regions. In this dual nano-phase amorphous structure, plasticity is mainly initiated through the elongation and coalescence of the amorphous nano-grains, resulting in a shear band much wider than in its monolithic counterpart. Consequently, the NGMG turns out to be softer at the microscopic scale. At the fundamental level, our finding provides a universal mechanism which explains the unusual strength weakening observed in a variety of dual nano-phase amorphous systems.