Microstructure evolution and mechanical properties of as-cast PdAgCuAuPt multi-principal elements alloy

The precious metals have attracted growing attention due to excellent comprehensive properties for contact materials in micro relays. In this work, a novel PdAgCuAuPt multi-principal elements alloy (MPEA) was investigated by combined CALPHAD calculation and experiments. The results show that the microstructure of as-cast PdAgCuAuPt MPEA exhibits a dual-phase face-centered cubic structure and the dendrites of (Cu, Pt)-rich FCC2 phase are surrounded by inter-dendritic region of (Ag, Au)-rich FCC1 phase. Two discontinuous phases of Au-Cu-rich and Au-Pt-rich lamellar phase and shrinkage porosities present in inter-dendritic grain boundaries. The microhardness of FCC1 phase is 17% higher than that of FCC2 phase. The soft and hard phases exhibit obvious inhomogeneity of composition and microstructure. The mechanical properties of as-cast PdAgCuAuPt MPEA includes an average yield strength of 388.3 MPa, an average ultimate tensile strength of 534.3 MPa and an average elongation of 28.0%.