TA15钛合金近β变形三态组织中片状α演化规律

Evolution Mechanism of Lamellar α in Tri-Modal Microstructure of TA15 Ti-Alloy during Near β Deformation

摘要:

近β变形+热处理工艺为TA15钛合金获得三态组织提供了一种可行途径，作为三态组织的重要组成部分并决定其损伤容限性能的片状α是在近β变形和后续热处理共同作用下产生的，其演化过程十分复杂，而三态组织对各相特别是片状α的含量和形态要求苛刻。本研究采用热模拟压缩实验和定量金相实验研究了不同近β变形条件下（变形温度、变形程度和应变速率）TA15钛合金变形+高低温强韧化热处理（950 ℃/100 min/WQ+800 ℃/8 h/AC）后微观组织演化行为，揭示了组织中片状α含量和形貌的演化规律；在此基础上，以高损伤容限性能为目标，研究确定了获得满足三态组织要求并具有优异断裂性能的片状α近β变形条件区间；实验和理论分析表明：针对TA15钛合金，在所确定的近β变形区间内可以获得性能优异的三态组织。研究结果可为TA15钛合金通过近β变形工艺获得三态组织和性能优化的片状α提供指导。

Abstract:

Near-β deformation combined with subsequent heat treatment process provides a possible way to obtain the tri-modal microstructure for TA15 Ti-alloy. As an important component of tri-modal microstructure, the evolution of lamellar α, which determines damage tolerance properties, is complex and difficult to control in the process of near β deformation and subsequent heat treatment. At the same time, the tri-modal microstructure has strict requirements on the composition and morphology of final microstructure, especially on lamellar α. In this paper the microstructure evolution behavior of TA15 Ti-alloy after deformation and 950 °C, 100 min, WQ+800 °C, 8 h, AC under different deformation conditions (deformation temperature, deformation degree and strain rate) were investigated via the thermal simulation test and metallographic test. The evolution mechanism of lamellar α in tri-modal microstructure was revealed. Based on the obtained results, taking high damage tolerance as target, the reasonable range of near β deformation condition were determined to obtain lamellar α possessing excellent fracture toughness and microstructure meeting requirement of tri-modal microstructure. Experimental and theoretical analyses show that for TA15 Ti-alloy the tri-modal microstructure of excellent performance could be obtained within the deformation condition range. The results can provide a guide for obtaining the tri-modal microstructure and excellent lamellar α via near-β deformation processing.