Analyzing the α2(Ti3Al) and B2 phases in high Nb-TiAl alloy sheets using mismatch theory

In this paper, high Nb-TiAl alloy sheets were fabricated via elemental foil metallurgy with the utilization of Ti foil, Al foil, and Nb foil. The results indicated that microstructure of the sheet primarily consisted of the α2(Ti3Al) phase, the γ(TiAl) phase, and the B2 phase. The B2 phase was present both at the grain boundaries and within the grains. The B2 phase could impede the movement of dislocations, which played a role in secondary phase strengthening. The mismatch between Ti3Al, B2 and TiAl phases were computed using one-dimensional and two-dimensional mismatch degree theories. The two-dimensional mismatch degree between γ(TiAl) and α2(Ti3Al) was 1.47%, and that between γ(TiAl) and B2/β phase was 2.65%. The results showed that the α2(Ti3Al) and B2 phases effectively facilitated the nucleation and growth of γ(TiAl) matrix phase. Specifically, the B2 phase, functioning as a precipitated phase, could hinder dislocation movement and impart a specific strengthening effect to the matrix.