Metastable phase formation during α_(2)(D0_(19)) to γ(L1_(0)) transformation in as-atomized γ-TiAl alloy powders

摘要

α_(2)(D0_(19)) to γ(L1_(0)) transformation during heating of as-atomized γ-TiAl powder was investigated by differential scanning calorimetry and x-ray diffraction. The as-atomized coarse powder particles (γ-TiAl powder: Ti-45Al-2Nb-0.7Mo-0.1W-2Cr-0.27O-0.2Si) with large amounts of retained α_(2) are a perfect candidate to investigate this transformation. It was observed that α_(2) to γ transformation is a two-step process involving the formation of a disordered face-centered-cubic γ′TiAl [with a(γ′)=c(γ)] as an intermediate phase followed by ordering.