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

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Thermal behavior and mechanical properties of Pd-based glassy alloys with compositions of Pd 35+x Cu 30 Ni 15-x P 20 (x = 0, 5, 7.5 at%, group-I) and Pd 40+x Cu 20 Ni 20-x P 20 (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 → Cu 3 Pd + Ni 2 Pd 2 P + Cu 3 Pd 5 P 2 + quaternary phosphide exists at a composition of approximately Pd 42.5 Cu 30 Ni 7.5 P 20 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%.