Microstructure and mechanical properties of high Nb containing TiAl alloys by reactive hot pressing

Microstructure and mechanical properties of Ti–45Al–8.5Nb–(W, B) (at.%) alloys fabricated by elemental powder metallurgy (EPM) were investigated. The results showed that microstructure hot pressed at 1300 °C is inhomogeneous for a few Nb particles are dispersed in Ti–Al matrix. With the increase of hot pressing temperature and sintering time, microstructure becomes more homogeneous. However, the diffusion of Nb is inhomogeneous at 1400 °C/0.5 h, and fully lamellar (FL) microstructure happens coarse at 1400 °C/2 h or 1500 °C/1 h. 1400 °C/1 h is an appropriate hot pressing process to fabricate high Nb containing TiAl alloys consisting of FL microstructure. Nb element dissolves into the Ti–Al matrix by diffusion, and pore nests form in situ. Hot isostatic pressing (HIP) treatment can only decrease porosity to some extent, but cannot eliminate pores completely. The compression strength of EPM high Nb containing TiAl alloy is higher, but its ductile is much worse than that of as-cast alloy.