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

Mechanical deformation of Pd40Ni40P20 was characterized in compression over a wide strain rate range (3.3 x 10(-5) to 2 x 10(3) s(-1)) at room temperature. The compression sample fractured with a shear plane inclined similar to42 degree with respect to the loading axis, in contrast to similar to56 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 (similar to1.74 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 similar to1.4 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 x 10(2) s(-1). These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate. (C) 2002 Elsevier Science Ltd. All rights reserved.