Abstract High temperature, large strain and fast strain rate resulting from the severe plastic deformation will cause local material instability, then physical and chemical reactions such as phase transition, grain redistribution and fracture may occur during this process. This paper presents an in-depth investigation about the material instability and corresponding microstructures during the serrated chip formation of titanium alloy Ti-6.5AL-2Zr-1Mo-1 V by high speed turning. Firstly, intense deformation during high speed cutting was verified. Phase transition under different loading conditions including temperature, strain and strain rate were also explored, followed by the domination of equiaxed α-phase due to suitably localized severe plastic deformation and sufficient cooling. Secondly, criterion for initiation of fracture of material was introduced and applied to chip breaking. Finally, particle redistribution phenomenon was analyzed accordingly and the so-called severe plastic flow was further verified.

中文翻译：

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钛合金Ti-6.5AL-2Zr-1Mo-1V高速车削局部剧烈塑性变形下的材料不稳定性

摘要 剧烈塑性变形产生的高温、大应变和快速应变速率会引起材料局部不稳定，在此过程中可能发生相变、晶粒再分布和断裂等物理化学反应。本文深入研究了钛合金 Ti-6.5AL-2Zr-1Mo-1 V 高速车削形成锯齿状切屑过程中的材料不稳定性和相应的微观结构。首先，验证了高速切削过程中的剧烈变形。还探索了不同加载条件下的相变，包括温度、应变和应变速率，然后由于适当局部严重塑性变形和充分冷却，等轴 α 相占主导地位。第二，引入了材料开始断裂的判据，并将其应用于断屑。最后，对颗粒再分布现象进行了相应的分析，进一步验证了所谓的剧烈塑性流动。