Research Progress on Variant Selection and Microstructural Characteristics of Martensitic Transformation of Titanium Alloys

In the practical production and processing of titanium alloys, variant selection frequently occurs during martensitic transformation due to various influencing factors. This preferential behavior causes the crystallographic orientation distribution of α′/α″ phases to deviate from theoretical equiprobability, consequently affecting material anisotropy and mechanical properties. Studies reveal that quenching-induced β→α′ transformation exhibits weak variant selection characteristics. In contrast, stress-induced β→α″ transformation often demonstrates strong variant selection effects with a consistent preference for orientations accommodating maximum external stress. Simultaneously, characteristic self-accommodating morphologies are commonly observed in α′/α″ martensitic microstructures, including triangular, V-shaped, Z-shaped, trapezoidal, and parallel clusters formed by aggregated variants. The emergence of these self-accommodating clusters is one of the critical mechanisms underlying variant selection effects. This paper systematically elaborates on the characteristics and formation mechanisms of martensitic transformation and elucidates the intrinsic nature and influencing factors of variant selection. By integrating the phenomenological theory of martensite and statistical analysis of inter-variant interfaces, the formation mechanisms of self-accommodating microstructures and interface distribution associated with variant selection effects are analyzed comprehensively. Finally, current challenges and future research priorities in this field are identified.