oa Effect of Hf on the Microstructure and Mechanical Property of Pt-15Ir-xHf-0.5Y Alloy

The influence of Hf content on the recrystallization and aging behavior of hot-rolled Pt-15Ir-xHf-0.5Y alloy was investigated by SEM, EBSD and hardness tests. The results show that the alloy texture evolves from a multi-peak one biased towards rolling direction-transverse direction (RD-TD) in the hot rolling state to a multi-peak one symmetrical along the normal direction (ND) after recrystallization annealing. The fibrous grains become equiaxial after recrystallization annealing, increase of Hf content refines the grains. Pt-15Ir-xHf-0.5Y alloy exhibits age-hardening behavior at the temperature range of 600°C~900°C, which is due to the precipitation of (Pt, Ir)5Y phase. Increasing Hf addition effectively improves the hardness through promoting the precipitated amount of (Pt, Ir)5Y phase. However, the internal oxidation within grain boundaries is deteriorated with the high-content Hf addition. The results of this study provide an insight into tailoring the microstructures and mechanical properties of the Pt-Ir high-temperature alloys.