Tailoring microstructure and mechanical performance of a β-solidifying TiAl alloy via martensitic transformation

Abstract This study aimed to tailor the microstructure and mechanical properties of a β-solidifying TiAl alloy via martensitic transformation. The as-cast microstructure of the applied alloy, Ti-42Al-8.5V (at. %), was characterized by large Widmanstatten colonies, forming the so-called “micro-textured” morphology. After oil-quenching from β phase field, martensitic transformation occurred so that most of the prior β phase was transformed into fine martensitic laths with various orientations. Although variant selection was noted in local regions, the micro-texture was evidently mitigated in comparison with the initial state. During the subsequent tempering processes, the martensite decomposed via α2′ → α2 + γ → β0 + γ, whereby two different microstructures were obtained. At lower tempering temperatures ( 900 °C), which was characterized by ultra-fine γ platelets embedded in the β0 matrix. Hot tensile tests revealed that the two microstructures had distinct mechanical properties. The former exhibited quite high strength at elevated temperatures and hence might be a candidate for high temperature service, while the latter was much softer and more suitable for thermo-mechanical processing.