Unveiling the role of glassy nanodomains in strength and plasticity of crystal–glass nanocomposites via atomistic simulation

Abstract

Crystalline metals and alloys are usually ductile owing to lattice dislocations and various slip systems, while bulk metallic glasses show ultrahigh yield strength with very limited plasticity. Combining the crystalline and glassy phases in one alloy has recently been shown to be promising for achieving both ultrahigh strength and good deformability. Yet, it is challenging to capture the dynamic dislocation behavior through the deformation process and elucidate the role of glassy domains on the excellent mechanical performance of the nanocomposites. Here, we unveil and visualize the atomic-scale interactions among dislocations, glassy nanodomains, and crystal–glass interfaces in a specially designed configuration via molecular dynamics simulation. The glassy nanodomains occupying the triple junctions of grain boundaries are found to optimize the dynamic partitioning of shear strains between the two phases, thus manipulating the production of both dislocations in the crystalline matrix and shear transformation zones in the glassy nanodomains. The crystal–glass interfaces where strain concentration can occur function as both dislocation sources and sinks for plasticity, which in turn alter the strain distributions in the two phases. Systematic observations further suggest that the glassy nanodomains can dynamically tune the dislocation content and configuration in the crystalline matrix throughout the deformation. The unveiled mechanisms thus open a pathway for the development of novel ultrahigh-strength and ductile materials by tuning dislocation behavior in the crystalline matrix via glassy nanodomains.