A high-Nb–TiAl alloy with ultrafine-grained structure fabricated by cryomilling and spark plasma sintering

In this work, an ultrafine-grained high-Nb–TiAl alloy with a nominal composition of Ti–45Al–8Nb–0.2W–0.2B (at%) was prepared by cryomilling and subsequent spark plasma sintering (SPS) technique. The chemical composition, particle size, morphology and crystallite size of cryomilled powder were studied. It is found that cryomilling can effectively reduce the particle size and enhance grain refinement. The ingots sintered at 900 and 1000 °C show an equiaxed near-γ microstructure with grain sizes < 700 nm, while the sample sintered at 1100 °C exhibits duplex microstructure. Especially, the one sintered at 1000 °C has excellent mechanical properties, whose compression yield strength, fracture strength, bending strength and plastic strain achieve 1310, 2174, 578 MPa and 16.8%, respectively. The reasons for the effect of cryomilling and the mechanical behavior of sintered ingots were discussed. It is suggested that cryomilling in combination with SPS is an effective way to synthesize high-Nb–TiAl alloy with ultrafine-grained structure.