Shear band network induced relaxation, hardening and uniform plastic deformation in metallic glass

Shear band networks, which cause strong interactions between shear bands and produce an effect similar to the grain refinements in polycrystalline metals, were introduced into a Zr-based metallic glass (MG) by a certain cycle of biaxial alternating compressions (BACs). Through experiments and molecular dynamics simulations, it was found that BACs can accumulate plastic strains in different directions, activate shear bands with different orientations, increase their intersecting probability, and ultimately induce the formation of shear band network. Unlike the softening observed during uniaxial deformation in many previous reports, the free volume first decreases and then increases with the number of BAC cycles. The reverse shear stresses during the BAC process will induce free volume annihilation, leading to a densification and significant hardening of MG. Due to the collaborative sliding of the complex shear band networks and the size effect induced by the restraints on newly formed shear bands from the networks, the plastic events become more difficult and their sizes become smaller, resulting in a work-hardening behavior in MG. Meanwhile, shear band networks also led to a quasi-uniform plastic deformation mode based on the cooperation of multiple shear bands.