SUPERPLASTICITY OF Nb-Si-Fe AND TiAl INTERMETALLICS SYNTHESIZED BY POWDER METALLURGY

摘要

Nb-16Si-2Fe alloy were processed by mechanical alloying (MA) and hot pressing sintering (HPS). Microstructure analysis revealed the presence of four phases: Nb solid solution (Nbss), three kinds of intermetallics Nb_3Si, Nb_5Si_3 and Nb_4Fe_3Si_5. The maximum elongation over 500% was obtained at 1450°C and strain rate of 2.31×10~(-1)s~(-1). TiAl powder pre-alloyed was carried out on pulse current sintering equipment (PCS) with high heating rate. The effect of heating rate on microstructures and high temperature ductility was investigated. The results show that relatively high heating rate is beneficial for obtaining fine grained microstructures. And the resultant intermetallic alloy with equiaxed near gamma structures exhibits superplasticity at relatively low temperature.