Microstructure and mechanical properties of Ti?45Al?8Nb alloy sintered at different SPS temperatures

Abstract:

In this paper, TiAl alloys with a nominal composition of Ti-45Al-8Nb (at.%) were prepared by spark plasma sintering (SPS) process. The effect of sintering temperatures on microstructure and mechanical properties of Ti-45Al-8Nb alloy has been studied. The results show that the microstructures of Ti-45Al-8Nb alloy sintered at different temperatures all exhibit full lamellae structure. With the increasing of sintered temperature, the amount of γ phase in the alloy increases and α₂ phase decreases. There is no B2 Phase when sintered at 1250℃. As the sintering temperature increases, the B2 phase precipitates at the grain boundary and the amount of B2 phase increases. The main reason is that the alloy may melt at local areas with the increasing of sintering temperature; the β phase would order to B2 phase at high cooling rates. The tensile strength and compression ratio decreases with the sintering temperature increasing from 1250℃ to 1300℃. The maximum tensile strength and compression ratio reached 2084.20MPa and 33.10% at 1250℃ respectively.

Key words:Spark Plasma Sintering (SPS); Ti-45Al-8Nb; pre-alloyed powder