The effect of heat treatment on the microstructure and mechanical properties of a novel α + β Ti-6.2Al-0.8V-2.25Mo-1.2Cr-0.5Si (wt%) alloy was investigated in this paper. Microstructure and crystalline structure of the alloys after different solution and aging treatments were identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that a multi-scale microstructure was possessed in the heat-treated samples, which was composed of equiaxed primary α (α_p) phase and nano-scale acicular secondary α (α_s). After 900 ℃ solution for 1 h and 550 ℃ aging for 6 h, the alloy exhibited the optimal combination of strength and ductility (the ultimate tensile strength of ∼1387 MPa, the elongation of ∼11 %). Furthermore, the combination mechanism of strength-ductility of the sample under this condition was investigated. The samples before and after tensile fracture were analyzed using transmission electron microscope (TEM) and electron back-scattered diffraction (EBSD). The results showed that a large proportion of nano-scale acicular α_s phases precipitated from the β matrix can effectively prevent the slip of dislocations and enhance the strength of the alloy. In addition, the multi-scale microstructure can create the strain partition, which can mediate the strain incompatibility between the α_p and the transformed β (β_T) to obtain an excellent combination of strength and ductility.

本文研究了热处理对新型 α + β Ti-6.2Al-0.8V-2.25Mo-1.2Cr-0.5Si (wt%) 合金的显微组织和力学性能的影响。通过扫描电子显微镜 (SEM) 和 X 射线衍射 (XRD) 鉴定了合金经过不同固溶和时效处理后的显微组织和晶体结构。结果表明，热处理后的样品具有多尺度的显微结构，由等轴初生α（α _p）相和纳米级针状次生α（α _s). 经过900℃固溶1h和550℃时效6h后，该合金表现出最佳的强度和延展性组合（极限抗拉强度~1387 MPa，延伸率~11%）。此外，研究了该条件下样品的强度-延展性组合机制。使用透射电子显微镜（TEM）和电子背散射衍射（EBSD）分析拉伸断裂前后的样品。结果表明，大量从β基体中析出的纳米级针状αs_相能有效阻止位错滑移，提高合金强度。此外，多尺度微结构可以产生应变分区，可以调节 α _{p之间的应变不相容性}和转化后的 β (β _T ) 以获得强度和延展性的完美结合。