阐明亚稳β钛合金中β相结构稳定性、微观组织演变与力学行为的相关性，是当前研究和发展兼具高强度与高塑性钛合金的关键科学问题。申请人前期探索研究发现，具有应力诱发逆ω相变和形变梯度孪晶的亚稳β钛合金Ti-4Mo-3Cr-1Fe可以兼具高强度（1.1 GPa）、高塑性（≥40%）及高加工硬化率（2.5 GPa），进一步揭示与其相关的相变、形变孪晶及力学行为的演化情况，对研发具有重要应用前景的高性能钛合金具有指导意义。本项目旨在深入研究具有不同β相结构稳定性的Ti-4Mo-3Cr-1Fe合金在单向应力作用下的微观组织演变，重点关注合金中应力诱发αʹʹ马氏体、ω相变与{332}<113>、{112}<111>形变孪晶的竞争与协作机制。在此基础上，明确合金的微观组织演变对力学性能的影响规律，揭示β相结构稳定性、微观组织演变与力学行为相关性的内在机制，为新一代高性能钛合金的设计和研发提供理论和技术基础。

The clarification of the correlation between the β phase stability of metastable β-Ti alloys, microstructural evolution and the mechanical behavior has been a key scientific issue for the investigation and development of advanced titanium alloys with high strength and high ductility. It was found in recent experimental study, high strength (1.1 GPa), high ductility (≥40%) and high strain-hardening rate (2.5 GPa) can be simultaneously achieved in the novel metastable β-Ti alloy Ti-4Mo-3Cr-1Fe with stress-induced reverse ω transformation and deformation hierarchical twins. It is of academic importance to clarify the relative mechanism to the phase transformation, deformation twins, the evolutions of microstructure and mechanical behavior, and of engineering significance to develop novel Ti alloys with low modulus. This project aims to investigate the microstructural evolution of Ti-4Mo-3Cr-1Fe alloy with various β phase stabilities under unidirectional stress, and especially focus on the competitive relationship and synergistic mechanism of the stress-induced phase transformation behavior of αʹʹ or ω and deformation twins of {332}<113> twinning or {112}<111> twinning, in attempt to clarify the relative mechanism of phase transformation, deformation twins and microstructural evolution. On this basis, the influence of microstructural evolution on the mechanical behavior of Ti-4Mo-3Cr-1Fe alloy will be studied, and the inherent mechanism of the β phase stability and microstructural evolution on the mechanical behavior in the novel metastable β-Ti alloy will be determined. The outcome of this project will promote the fundamental research on the microstructural control and the optimization of mechanical performance, providing a significant theoretical and technological basis for the development of new generation high performance titanium alloys.