Abstract One of the most critical aspects in understanding the deformation behavior of two-phase titanium alloys subjected to thermomechanical processes (TMPs) lies in being able to describe the flow stress accurately. To this end, in this study, initially, hot tension tests were conducted on a two-phase Ti-6Al-2Zr-1Mo-1V alloy. It was observed that the flow stress at a given temperature and strain rate exhibits work hardening, followed by flow softening. Flow softening occurs at the peak strain, where the maximum stress is observed; peak strain decreases with increasing temperature and decreasing strain rate. Variations in peak strain are more obvious at low temperatures and high strain rates. Later, the microstructure of the alloy was analyzed and the results show that work hardening and flow softening are caused by dynamic recrystallization (DRX). The DRX volume fraction was found to exhibit an increasing trend and discontinuous dynamic recrystallization (DDRX) was observed at increasing temperature and decreasing strain rate. With respect to microstructure evolution, a unified model consisting of a thermally activated stress component and an athermal stress component was developed. In the athermal stress term, dislocation density and the Hall-Petch effect were used to describe the work-hardening and flow-softening behavior. In the case of the dislocation term, the DRX effects were modeled considering the critical strain for DRX initiation and the DRX rate, which are both temperature-and strain rate-dependent. In the Hall-Petch effect term, the dependence of the Hall-Petch coefficient on the processing conditions was considered and the loss of Hall-Petch strengthening with deformation was modeled. Using the proposed model, the work-hardening and flow-softening behavior and microstructure evolution in Ti-6Al-2Zr-1Mo-1V alloys subjected to TMP were predicted. A good agreement could be observed between the experimental and predicted results. This study provides a solution for modeling work-hardening and flow-softening behavior and helps us understand the deformation behavior of two-phase titanium alloys subjected to TMP.

中文翻译：

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考虑热机械过程中微观结构演变的两相钛合金加工硬化和流动软化的统一建模

摘要 理解两相钛合金在热机械过程 (TMP) 下的变形行为最关键的方面之一在于能够准确地描述流变应力。为此，在本研究中，最初对两相 Ti-6Al-2Zr-1Mo-1V 合金进行了热拉伸试验。观察到在给定温度和应变速率下的流动应力表现出加工硬化，然后是流动软化。流动软化发生在峰值应变处，在此处观察到最大应力；峰值应变随温度升高和应变速率降低而减小。峰值应变的变化在低温和高应变率下更为明显。之后，分析了合金的显微组织，结果表明加工硬化和流动软化是由动态再结晶（DRX）引起的。发现 DRX 体积分数呈现增加趋势，并且在升高温度和降低应变速率下观察到不连续动态再结晶 (DDRX)。关于微观结构演化，开发了由热激活应力分量和非热应力分量组成的统一模型。在非热应力项中，位错密度和霍尔-佩奇效应用于描述加工硬化和流动软化行为。在位错项的情况下，考虑到 DRX 引发的临界应变和 DRX 速率，对 DRX 效应进行建模，这两者都依赖于温度和应变速率。在霍尔-佩奇效应项中，考虑了 Hall-Petch 系数对加工条件的依赖性，并模拟了 Hall-Petch 强化与变形的损失。使用所提出的模型，预测了经过 TMP 处理的 Ti-6Al-2Zr-1Mo-1V 合金的加工硬化和流动软化行为以及微观结构演变。在实验结果和预测结果之间可以观察到很好的一致性。这项研究为模拟加工硬化和流动软化行为提供了解决方案，并帮助我们了解两相钛合金在 TMP 下的变形行为。预测了经过 TMP 处理的 Ti-6Al-2Zr-1Mo-1V 合金的加工硬化和流动软化行为以及微观结构演变。在实验结果和预测结果之间可以观察到很好的一致性。这项研究为模拟加工硬化和流动软化行为提供了解决方案，并帮助我们了解两相钛合金在 TMP 下的变形行为。预测了经过 TMP 处理的 Ti-6Al-2Zr-1Mo-1V 合金的加工硬化和流动软化行为以及微观结构演变。在实验结果和预测结果之间可以观察到很好的一致性。这项研究为模拟加工硬化和流动软化行为提供了解决方案，并帮助我们了解两相钛合金在 TMP 下的变形行为。