Realizing Strength and Plasticity Balance of Selective Laser Melting Fabricated Ti-6Al-4V Alloy through Multi-stage Heat Treatment

Selective laser melting (SLM) manufacturing of Ti-6Al-4V alloy typically exhibits high strength and low ductility, requiring heat treatment to decompose acicular α′ martensite into balanced α+β phases to achieve excellent mechanical properties. Based on optimizing SLM forming process parameters, this study systematically investigated the effect of multi-stage heat treatment on the microstructure and tensile properties of Ti-6Al-4V alloy. The experimental results demonstrated that the Ti-6Al-4V alloy fabricated through SLM exhibits a relative density of 99.66% under the optimal process parameters. After undergoing stress relieving, solution-aging, and hot isostatic pressing treatments, the Ti-6Al-4V alloy obtained a Widmanstädter structure consisting of α colony within nearly equiaxed β grains. In comparison to the acicular α′ martensite within the columnar β grains of SLM-manufactured Ti-6Al-4V alloy, the yield strength and tensile strength decreased by 252 MPa and 312 MPa, respectively, while the elongation at break increased by 8-9%. The tensile properties meet the requirements of ASTM F2924-14, achieving a balance between strength and ductility.