Zr-1.0Ti-0.35Nb合金热变形行为研究

Investigations on Hot Deformation Behavior of Zr-1.0Ti-0.35Nb Alloy

乏燃料后处理强酸、强氧化性、强放射性的工作环境,对后处理溶解器选材、加工工艺提出了严苛要求。本工作研究了自主设计Zr-1.0Ti-0.35Nb合金在670~750℃温度范围、3种不同应变速率0.01、0.1和1 s^(-1)条件下的热压缩变形行为,分析了热压缩过程中该合金的微观组织特征,并基于峰值应力构建了其热变形本构模型。结果表明,应变速率和变形温度对Zr-1.0Ti-0.35Nb合金热变形过程具有显著影响,流变应力随应变速率增加而增大,随变形温度的升高而减小,达到峰值应力后流变曲线呈现明显动态再结晶特征;提高变形温度有助于发生动态再结晶和晶粒长大;基于Arrhenius本构方程计算得到Zr-1.0Ti-0.35Nb合金的热变形激活能为225.8kJ/mol,硬化指数为5.62,说明合金元素Ti使锆合金的热变形激活能升高;实验值与预测值之间的相关系数为0.97427,平均相对误差为6.15%,证实此本构方程预测Zr-1.0Ti-0.35Nb合金流变应力的准确性,能够为新型锆合金热加工工艺优化提供理论指导。

The harsh environment with strong acid,high oxidability and irradiation raises urgent demand for advanced structural materials used for reprocessing dissolver of spent nuclear fuels.In this paper,hot compression behavior of a Zr-1.0Ti-0.35Nb alloy was investigated at the strain rate of 0.01,0.1,1 s^(-1) and in the temperature range of 670-750℃.Microstructural evolution during the hot compression was analyzed.The results reveal that the strain rate and deformation temperature both significantly affect the hot deformation behavior of Zr-1.0Ti-0.35Nb alloy.Flow stress increases with the accelerated strain rate and decreases with the elevated temperature.Beyond peak stress,the flow curve exhibits apparent dynamic recrystallization characteristics.Elevated deformation temperature favors dynamic recrystallization and grain growth.An Arrhenius-type constitutive model was established based on the obtained peak stress values,in which the activation energy is calculated as 225.8 kJ/mol,suggesting a Ti-induced elevation of activation energy and the hardening index is 5.62.A correlation coefficient of 0.97427 and average relative error of 6.15%are obtained between the experimental and predicted values,demonstrating sound applicability of the constitutive model that is expected to guide processing optimization for the new Zr-1.0Ti-0.35Nb alloy.