Hydrostatic pressure effect on metallic glasses: A theoretical prediction

Metallic glasses are topologically disordered down to the atomic scales. As a result, during mechanical deformation there are random atomic displacements which necessarily lead to the volume change. Although volume dilatation has been observed, its contribution to the mechanical deformation and the pressure sensitivity in the yielding and fracture strengths remains controversial; since volume is the thermodynamic conjugate variable to the hydrostatic pressure, the volume change must be accompanied by certain degrees of pressure sensitivity. However, among the available measurements, a negligible effect of pressure on the yielding and fracture strengths is reported. Here, we try to understand this exceptional case. By using a finite deformation theory, we analyze the pressure effect on metallic glasses simultaneously subject to a pure shear and an applied hydrostatic pressure. We show that the shear deformation does couple to pressure, which is manifested through a strong dependence of the shear strength on pressure. We argue that the tendency of the deformation localization and the omnipresent sample imperfections may be responsible for the discrepancy between the available experimental results and our theoretical predictions. Published under license by AIP Publishing.