Mechanical cycling-induced evolution of structure and local mechanical properties in a PdCuNiP bulk metallic glass

Abstract

To improve the ductility of bulk metallic glasses (BMGs), external mechanical stimulations can be applied. Thereby, cyclically loading the samples at stress levels below the macroscopic elastic limit leads to permanent structural changes, which can alter the plasticity in bulk metallic glasses. Here, the effect of systematic variations of Pd43Cu27Ni10P20 BMG's structural state, achieved through cyclically loading the material to 70, 80, and 90% of the yield strength, on a range of mechanical properties like modulus, hardness, yield strength, strain rate sensitivity, activation volume, maximum shear stress and stiffness at different probing volume is studied. It is observed that samples rejuvenated from the non-cycled state to the 70% of yield stress state, relaxed when cycled up to 80% of yield stress, and finally rejuvenated again when cycled up to 90% of yield stress. This rejuvenation to relaxation transition might be due to the random atomic rearrangement during the cycling.