First-Principles Study on the Effect of Ir Doping on the Mechanical and Thermodynamic Properties of Pt–20Rh Alloy

Ir doping is an effective method used to strengthen and toughen Pt–Rh alloy and improve its high-temperature properties. However, Ir and Pt–Rh alloys are infinite solid solution alloys, and their microstructures are difficult to observe to understand their mechanism of action. Therefore, the stability and mechanical and thermal properties of a series of Pt–20Rh–xIr ( x = 0, 5, 10 and 20) alloys were calculated using first-principle studies based on density functional theory. The results show that with an increase in the Ir content, the Young’s modulus and hardness of Pt–20Rh–xIr initially decrease and then increase. The largest Young’s modulus (436.243 GPa) and hardness (18.453 GPa) were achieved when the Ir content was 20 wt%. Meanwhile, the thermodynamic calculation results show that with an increase in the Ir content, the thermal stability of Pt–20Rh–xIr was significantly improved, and the thermal expansion coefficient of Pt–20Rh–xIr was only 63% of that observed for Pt–20Rh. The above results imply that the addition of 20 wt% Ir gave the best effect on improving the strength, toughness and high temperature properties of Pt–20Rh alloy. This study provides theoretical guidance for further application of Pt–Rh alloy in the aviation field.