Hydrostatic Pressure Effect on Metallic Glasses: Finite Deformation Theory

Metallic glass does not have well-defined atomic planes and the related dislocation motion during plastic deformation. The atomic displacement during deformation instead contains a large degree of randomness, which necessarily leads to volume change. However, how the volume change contributes to the mechanisms of mechanical deformation, especially the pressure sensitivity of yielding and fracture strength remains unclear. Although volume dilatation has been observed in various mechanical deformation, experimental investigation so far shows negligible pressure effect on yield and fracture strength. Here using finite deformation theory, we give a theoretical analysis of the pressure effect on metallic glasses subject to pure shear in the presence of a large range of applied hydrostatic pressure. We found that shear deformation does couple to applied pressure as manifested through the dependence of shear strength on applied hydrostatic pressure. We argue that the strong tendency of deformation localization and the omnipresent sample imperfections unique for amorphous solids may cause the discrepancy between the theoretical and experimental results.