The Ti–6.5Al–2Zr–1Mo–1V (TA15) alloy fabricated by laser powder bed fusion (LPBF) generally exhibits high strength but limited ductility, mainly owing to the dominance of α' martensite within coarse columnar prior-β grains. Achieving effective microstructure refinement via feasible and cost-effective heat treatment remains a critical goal for improving ductility. However, conventional heat treatment routines often lead to coarser α lath structures relative to the as-built martensite or require complicated processing routes. In this work, using a simple one-step annealing treatment, we successfully refined the microstructure of LPBF-fabricated TA15 alloy, significantly enhancing ductility with only a minor loss in strength. Following annealing at 800∼850 °C for 2 h and subsequent furnace cooling, a well-refined lamellar α+β microstructure was obtained. Compared with furnace cooling, water quenching further tailors the retained β phase into distinct layers of considerable thickness. This refined microstructure delivers an excellent strength–ductility synergy: a tensile strength of 1058 MPa accompanied by a ductility of 20.4%, far exceeding the 10.2% elongation of the as-built alloy. Such abnormal microstructure refinement during single-step annealing is attributed to the temperature-dependent competition between α′ martensite decomposition and thermal coarsening. Specifically, within 800∼850 °C, the decomposition of α′ martensite plays a dominant role in microstructure evolution, giving rise to lamellar refinement. This work demonstrates that a simple one-step annealing process can effectively regulate the as-built microstructure and achieve an outstanding mechanical balance, providing a practical and efficient approach for optimizing the mechanical performance of LPBF-manufactured TA15 components.
Shi et al. (2026) studied this question.