Effect of strain rate on compressive behavior of a Pd40Ni40P20 bulk metallic glass

Abstract

Mechanical deformation of Pd40Ni40P20 was characterized in compression over a wide strain rate range (3.3×10−5 to 2×103 s−1) at room temperature. The compression sample fractured with a shear plane inclined ∼42 degree with respect to the loading axis, in contrast to ∼56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (∼1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about ∼1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×102 s−1. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate.