Abstract The effect of deformation temperature on microstructure evolution and mechanical properties of a near α titanium alloy during isothermal multiple die forging (IMDF) is systematically investigated. Present study describes the grain refinement mechanism at different deformation temperature by electron back-scatter diffraction (EBSD) characterization. The results indicated that the grain refinement as a result of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). With the decrease of deformation temperature, the mechanism of DRX converts from DDRX to CDRX. The formation of new grains by CDRX mechanism is mainly attributed to the progressive rotation of sub-grains. Moreover, the fresh grains resulted from DDRX process form along the serrated grain boundaries by bulging. It indicates that the superior tensile strengths of the IMDFed titanium alloy at room temperature (RT) and 650 °C are attributed to grain boundary strengthening and dislocation strengthening. However, grain boundary strengthening no longer works above 650 °C, leading to rapid decreases in tensile strengths.

中文翻译：

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剧烈塑性变形近α高温钛合金动态再结晶机理及力学性能改善

摘要 系统研究了变形温度对等温多模锻（IMDF）过程中近α钛合金组织演变和力学性能的影响。目前的研究通过电子背散射衍射 (EBSD) 表征描述了不同变形温度下的晶粒细化机制。结果表明，晶粒细化是连续动态再结晶（CDRX）和不连续动态再结晶（DDRX）的结果。随着变形温度的降低，DRX的机理由DDRX转变为CDRX。CDRX机制形成的新晶粒主要归因于亚晶粒的渐进旋转。此外，DDRX 工艺产生的新鲜晶粒通过鼓胀沿锯齿状晶界形成。这表明 IMDF 钛合金在室温 (RT) 和 650 °C 下的优异拉伸强度归因于晶界强化和位错强化。然而，晶界强化在 650 °C 以上不再起作用，导致抗拉强度迅速下降。