Microstructural evolution and nanoindentation creep behavior in a PdAgCuAuPtZn multi-principal elements alloy

Abstract

The precious metal based multi-principal elements alloy (MPEA) PdAgCuAuPtZn is mainly used in electrical contact applications, as a new type of multi-component alloy. However, there is a lack of detailed information about the precipitation evolution and its effect on the creep properties of the PdAgCuAuPtZn alloys. Combining nanoindentation and detailed electron microscopy analyses, we investigated the microstructural evolution and creep mechanism of the Pd–30Ag–14Cu–10Au–10Pt–1Zn alloy during aging treatment systematically. Microstructural analyses show that discontinuous precipitation (DP) with Cu-rich and Ag-rich phases is observed in aging-treated samples. As the aging temperature increases, DP gradually replaces the matrix and coarsens. Meanwhile, the grain size gradually decreases because of the existence of DP. Spinodal decomposition (SD) and chemical short-range order (CSRO) can be observed in the matrix and CSRO can be observed in the Cu-rich phase. Nanoindentation results show that when the aging temperature is below 500 °C, the matrix and DP hardness gradually increase, from 4.06 GPa to 7.42 GPa and 3.78 GPa–5.29 GPa, respectively, and gradually decreases at temperatures higher than 500 °C. Based on the creep displacement analysis, the increasing temperature contributes to improving the creep resistance and DP has higher creep resistance than matrix. The results of the creep stress exponent (n) and activation volume (V) also indicate that the creep mechanism is dominated by dislocation movement. Both CSRO and SD contribute to improving creep resistance. These results will be beneficial to both deeply understanding the creep behavior of PdAgCuAuPtZn alloys and designing high-performance precious metal multi-component alloys.

Keywords

• Precious metals MPEA
• Nanoindentation creep behavior
• Discontinuous precipitation
• Chemical short-range order
• Spinodal decomposition