A strain-transformable microstructure was successfully designed in a metastable β Ti–7Mo–3Nb–3Cr–3Al alloy with enhanced mechanical properties, by introducing ∼28% α precipitates coupled with the TRIP effect, overcoming the traditional trade-off dilemma between strength and ductility in most metastable β-Ti alloys. The as-designed lamellar microstructure was predominantly deformed by stress-induced martensitic (SIM α") phase transformations, martensitic twinning and dislocation slip of the parent β grains and α laths. The β→α" transformation followed the [113]_β//[112]_α"//[-310]_α"//[1-21]_α" orientation relationship, with the {133}_β habit plane predicted by the Phenomenological Theory of Martensite Crystallography (PTMC). A novel <211>_α" type II martensitic twinning mode was also found, in addition to the {111}_α" type I mode at SIM α"/α impinging region. The results show that, not only the lamellar α precipitates play a major role in precipitation strengthening, but they can also effectively block SIM α" propagation at the initial stages of deformation. However, SIM α" transmission across the α laths was also observed for large strains. Moreover, <c+a> pyramidal slip and shear of the α laths also contributed to the accommodation of internal stresses. Therefore, the origin of the enhanced tensile mechanical properties can be attributed to the combined effects of α precipitation strengthening coupled with the TRIP softening effect and the extra interaction stresses introduced by the α laths and other deformation products, validating the design concept. The current investigation may provide a novel strategy for designing new high-performance metastable β-Ti alloys.

通过引入约 28% 的 α 析出物并结合 TRIP 效应，成功地在具有增强机械性能的亚稳 β Ti-7Mo-3Nb-3Cr-3Al 合金中设计了应变可转换的微观结构，克服了传统的强度和强度之间的权衡困境。大多数亚稳态 β-Ti 合金的延展性。所设计的层状显微组织主要通过应力诱发马氏体 (SIM α") 相变、马氏体孪晶和母体 β 晶粒和 α 板条的位错滑移而变形。β→α" 转变遵循 [113] _β // [112] _α" //[-310] _α" //[1-21] _α"方向关系，与{133} _β马氏体晶体学现象学理论 (PTMC) 预测的习性平面。在 SIM α"/α 撞击区，除了 {111} _α" I 型外，还发现了一种新的 <211> _α" II 型马氏体孪晶模式。结果表明，不仅层状 α 相析出强化的主要作用，但它们也可以有效地阻止 SIM α" 在变形初始阶段的传播。然而，对于大应变，也观察到 SIM α" 在 α 板条上的传输。此外，< c + a> α 板条的锥体滑移和剪切也有助于调节内应力。因此，增强的拉伸力学性能的起源可以归因于α沉淀强化与TRIP软化效应以及α板条和其他变形产物引入的额外相互作用应力的综合作用，验证了设计理念。目前的研究可能为设计新的高性能亚稳态 β-Ti 合金提供一种新策略。