電子ビーム溶融法によって作製されたチタンアルミ合金の機械的特性に及ぼすα₂相の形態の影響

抄録

This study was conducted to reveal the relationship between the α₂ phase morphology and the mechanical properties of Ti-48Al-2Cr-2Nb fabricated by electron beam melting (EBM). Tensile and creep tests were conducted for three kinds of samples: an as-HIP (hot isostatic pressing) sample and samples heat-treated at 1300°C and 1400°C after HIP. The microstructure observation in the as-HIP sample showed duplex-like structure/γ band layers formed by the EBM process. The HIP-1300 sample consisted of γ single grains, blocky α₂ phase grains, and α₂/γ lamellar grains with decomposed α₂ lamellas. The tensile properties and creep resistance of the HIP-1300 sample were inferior to those of the as-HIP sample because the α₂/γ interfaces of the blocky α₂ phase were incoherent. The HIP-1400 sample, which had fully lamellar structure, was fractured in the elastic region, although this sampleʼs creep resistance and life were superior to those of the other samples due to the lamellar interfaces, coarse grains, and zig-zag grain boundaries.