An ultra-high temperature Pt-15Ir-3Hf-0.5Y alloy with high hardness and tensile strength achieved by hot rolling and ageing treatment

Abstract

A novel ultra-high temperature Pt-15Ir-3Hf-0.5Y (wt.%) alloy was developed for the first time by high vacuum arc-melting, hot rolling and ageing treatment. The microstructures of the as-cast and hot-rolled and then post-aged samples were investigated. The alloy consists of the (Pt,Ir)5Y phase and matrix. Through transmission electron microscopy atomic resolution imaging, three types of nanoclusters, clusters containing stacking fault, clusters at 1/2 〈011〉 dislocation core and clusters with short-range order were observed in the matrix. The hardness at the ambient temperature of the alloy after hot rolling and ageing treatment was up to 443 HV and the tensile strength at 1500 °C was up to 47.8 MPa. Compared with the solid solution strengthened Pt-Ir binary alloys, the addition of Hf and Y can effectively improve the mechanical properties, which were achieved by introducing the combined effects of nanocluster strengthening and grain boundary strengthening of (Pt,Ir)5Y phase. Our findings provided new insights into designing the Pt-based superalloy with high strength and ductility.

Keywords

• Pt-Ir alloy
• Precipitate microstructure
• Mechanical properties
• Transmission electron microscopy