Deformation and Fracture Behaviors of Pd-Cu-Ni-P Glassy Alloys

Abstract

Thermal behavior and mechanical properties of Pd-based glassy alloys with compositions of Pd_35+xCu₃₀Ni_15−xP₂₀ (x=0, 5, 7.5 at%, group-I) and Pd_40+xCu₂₀Ni_20−xP₂₀ (x=0, 5, 10 at%, group-II) have been studied. Group-I alloys lie in an invariant eutectic reaction region of the quaternary system. The invariant eutectic reaction of L→Cu₃Pd+Ni₂Pd₂P+Cu₃Pd₅P₂+quaternary phosphide exists at a composition of approximately Pd_42.5Cu₃₀Ni_7.5P₂₀ and at a temperature of about 800 K . Both group glasses possess a large supercooled liquid region of over 80 K before crystallization. The compressive strength, Young’s modulus and Vickers hardness in each group increase with increasing Ni content. The compressive fracture strength and Young’s modulus are in the range of 1610 to 1740 MPa and 100 to 110 GPa, respectively. Under a uniaxial compression mode, these glassy alloys deformed inhomogeneously and fractured adiabatically. No distinct plastic deformation was observed for group-I alloys, while group-II alloys exhibited serrated flow with a maximum plastic strain of about 1.3%.