Ti6321(Ti-6Al-3Nb-2Cr-1Mo)合金广泛应用于船舶与海洋工程装备，但该合金在热变形时复杂的微观组织演变机制为形性一体化制造带来了困难， 阐明 Ti6321 合金的流变行为和变形机制将为后续在复杂的热变形条件下制造出满足成形质量和组织性能要求的 Ti6321 合金结构件提供理论指导。 本研究针对 Ti6321 钛合金在热加工中动态软化机制不明确的问题，通过等温热压缩实验，结合 SEM 与 EBSD 技术，系统分析了其在 α+β 相区(850~950 ℃)的流变行为及微观组织演变规律。 结果表明，合金流变曲线呈现典型加工硬化与动态软化交替特征，峰值应力随温度降低或应变速率升高而显著增加。 动态再结晶机制以不连续动态再结晶为主，晶粒沿变形晶界弓出形核形成 " 项链状 " 结构，而连续动态再结晶通过亚晶旋转和聚合实现，其对流变软化的贡献较小。 变形温度升高促进 β 相形成，抑制动态再结晶，导致晶粒粗化。 此外，高温下晶界取向差角分布与相重构法证实了动态相变的发生。 研究揭示了 Ti6321 合金在热变形过程中，动态再结晶与动态相变耦合的软化机制。

Ti6321(Ti-6Al-3Nb-2Cr-1Mo) alloys are widely employed in ships and marine engineering equipment. However, the complex microstructural evolution mechanisms of this alloy during hot deformation present significant challenges for integrated forming and performance-oriented manufacturing. A comprehensive understanding of its flow behavior and deformation mechanisms is essential to provide theoretical guidance for the manufacturing of Ti6321 alloy structural components that satisfy both the forming quality and microstructural performance requirements under complex hot deformation conditions. To clarify the dynamic softening mechanisms of the Ti6321 titanium alloy during hot deformation, isothermal hot compression tests were performed, combined with SEM and EBSD analyses. The flow behavior and microstructural evolution in the α+β phase region (850~950 ℃)were systematically investigated. The results indicate that the flow curves of the alloy display typical alternating work hardening and dynamic softening characteristics. The peak stress increases significantly with decreasing temperature or increasing strain rate. The dynamic recrystallization mechanism

is dominated by discontinuous dynamic recrystallization, characterized by grain nucleation along deformed grain boundaries to form “necklace-like” structures, whereas continuous dynamic recrystallization through subgrain rotation and coalescence makes a relatively minor contribution to flow softening. Higher deformation temperatures promote β phase formation, suppress dynamic recrystallization, and result in grain coarsening. Furthermore, the distribution of grain boundary misorientation angles and phase reconstruction analysis at elevated temperatures confirmes the occurrence of dynamic phase transformation. Finally, the coupled softening mechanisms of dynamic recrystallization and dynamic phase transformation during the hot deformation of the Ti6321 alloy are elucidated.