Effects of heat treatment on the microstructural evolution and creep behavior of the Ti-46Al-2Zr-2Cr alloy

This study systematically investigates the effects of two distinct heat treatment regimes on the microstructural evolution and creep behavior of the Ti-46Al-2Zr-2Cr alloy. During heat treatment in the (α+γ) phase field (1250 °C/2 h/FC, HT1), the fraction of blocky γ phase (γ_b) significantly increases, accompanied by the redistribution of Zr. Conversely, during heat treatment in the α phase field (1350 °C/0.5 h/FC, HT2), the residual Zr-rich γ_b phase retained after the short holding time leads to a nearly lamellar microstructure. Compared to the as-cast (AC) sample, the HT1 sample exhibits inferior creep resistance, while the HT2 sample displays superior creep resistance. The creep stress exponent ( n ) values for the AC, HT1, and HT2 samples are determined to be 3.32, 3.52, and 3.47, respectively. TEM observations suggest that the creep deformation of the experimental alloys at 800 °C is predominantly governed by dislocation glide, with mechanical twinning serving an auxiliary role. For both the AC and HT1 samples, crack initiation and propagation primarily occur at the γ_b phase interface during creep. Notably, the HT1 sample exhibits a more rapid progression of creep failure due to its higher fraction of the γ_b phase. In contrast, for the HT2 sample, cracks preferentially initiate at the B2/γ interfaces and propagate along adjacent grain boundaries.