Effects of Various Heat Treatments on Room- and High-Temperature Tensile Properties of Ti65 Alloy Fabricated via Electron Beam Powder Bed Fusion

Ti65 is a promising structural material for lightweight high-temperature aerospace components, yet the heat-treatment response of Ti65 fabricated by electron beam powder bed fusion (EB-PBF) remains insufficiently understood. In this study, EB-PBF Ti65 specimens were subjected to solution treatments at 800–1000 °C for different holding times followed by aging at 650 °C for 2–8 h. Microstructural evolution was characterized and tensile properties were evaluated at room temperature and 650 °C along the XY and Z directions. The as-built alloy exhibited a fine basketweave α + β lamellar microstructure with evident anisotropy. Increasing the solution temperature promoted α-lamella dissolution, elemental homogenization, discontinuity of grain-boundary α, and microstructural reconstruction. The 1000 °C/2 h + 650 °C/2 h treatment significantly improved room-temperature strength and transverse ductility, giving ultimate tensile strengths of approximately 1050 MPa and reducing anisotropy. At 650 °C, all specimens showed reduced strength but increased ductility; low-temperature solution treatment favored ductility, whereas 1000 °C-based treatments combined with appropriate aging improved elevated-temperature strength. Aging for 4 h provided a balanced strength–ductility combination, while longer aging enhanced yield strength but reduced ductility. These results demonstrate that tailoring solution and aging parameters is essential for optimizing the microstructure and mechanical performance of EB-PBF Ti65 alloy. Specifically, the 1000 °C/2 h + 650 °C/2–4 h regime achieved UTS of ~1050 MPa at room temperature and ~608 MPa at 650 °C, with XY-direction elongation increasing from 5.4% to 11.5%, representing a quantitative anisotropy reduction of approximately 53%.