Microstructure and properties of beta Ti-Nb alloy prepared by powder metallurgy route using titanium hydride powder

In the present work, Ti-40 mass%Nb alloys were successfully fabricated by a powder metallurgy route consisting of mechanical alloying (MA) of TiH2-Nb powder mixture and spark plasma sintering (SPS). The use of brittle TiH2 powder, instead of ductile elemental powder, led to significant increment in the yield of mechanically alloyed (MAed) powder. The MAed powder consisted of homogeneously distributed nano-sized Ti/Nb hydride particles together with micron-sized pure Nb particles. The MA also led to the lowering of dehydrogenation temperature of hydride particles. Sintering of MAed powders under low temperature conditions (1223 K, & 1373 K) resulted in the fine-grained heterogeneous microstructure consisting of alpha, beta, and unreacted pure Nb phase. On the other hand, sintering at higher temperatures (1523 K) resulted in a relatively coarse-grained chemically homogeneous microstructure with almost complete beta phase. Coarse-grained homogeneous beta Ti-Nb alloy exhibited higher average hardness as compared to that of heterogeneous fine grained microstructures. An attempt has been made to illustrate the correlation between the microstructural characteristics and mechanical properties of the sintered Ti-40Nb compacts. (C) 2015 Elsevier B.V. All rights reserved.