Achieving high performance HPS TiAl based alloy by adjusting sintering process parameters to eliminate heterogeneous microstructure and original powder boundaries

The influence of sintering parameters on the microstructural evolution and mechanical properties of Ti-46.5Al-2Cr-1.8Nb-0.2W-0.15B (at.%) alloys fabricated via hot press sintering by adopting pre-alloyed powders are investigated in detail. The results indicated that the alloys were composed of heterogeneous microstructure caused by localized recrystallization and original powder boundaries (OPBs), when densified at insufficient sintering parameters. Hence, the alloys cracked at the interface of heterogeneoum icrostructure or OPBs due to the discontinuity of deformation, resulting in a relative low mechanical property at 800 °C and the hot workability. With increasing the sintering temperature and holding time to 1300 °C and 120min, respectively, the OPBs and heterogeneous microstructure faded away, and the fracture mechanism transformed into micro-void development at the interfaces of deformation twin groups and the DRX grains, which lead to the increase of plasticity. Further increasing the sintering temperature or holding time, the comprehensive mechanical properties decreased due to the coarsening of microstructure. Therefore, the optimal sintering parameters were considered as sintering at 1300 °C with a holding time of 120min. This research can provide a scientific reference for the preparation of high-performance TiAl based alloys by powder metallurgy method.