动态拉伸下TA2纯钛的Taylor-Quinney系数研究

Taylor-Quinney Coefficient of TA2 Pure Titanium Under Dynamic Tension

金属塑性热耗散仍是一个未完全解决的问题,如现有文献中关于功-热转换系数及其应变、应变率相关性的实验结果并不一致。本研究对TA2工业纯钛在0.1~100s^(-1)应变率下拉伸过程的热耗散特性开展研究,采用数字图像相关法(DIC)及红外测温同步测试系统对平板拉伸试样的变形及温度场演化过程进行分析。结果表明,当应变率大于1 s^(-1)时,在试样拉伸颈缩前,可近似为绝热状态。TA2工业纯钛的Taylor-Quinney系数β的应变率效应不敏感,但并不是一个常数,而是随应变演化的。在加载初始阶段β随应变增大而增大,至拉伸应变0.08左右时达到最大值0.92;随后β随应变发展逐渐减小,至应变0.3时β减小为0.8左右。不同变形阶段试样的EBSD微观分析表明,Taylor-Quinney系数的变化与材料变形过程孪晶及微观组织演化相关。

Metal plastic heat dissipation is still an unsolved problem.For example,the experimental results of the work-heat conversion coefficient and its strain and strain rate correlations are not consistent in the existing literatures.The heat dissipation characteristics of commercial purity titanium TA2 during tensile process were studied at 0.1-100 s^(-1) strain rate.Digital image correlation(DIC) and infrared temperature measurement synchronous test system were used to analyze the deformation and temperature field evolution of plate tensile specimens.The results show that when the strain rate is greater than 1 s^(-1),the sample is approximately adiabatic before tensile necking.The Taylor-Quinney coefficient β of TA2 is not sensitive to the strain rate effect,which is not a constant and evolves with strain.In the initial stage of loading,β increases with the increase in strain,and reaches the maximum value of 0.92 when the tensile strain is about 0.08.Then,β decreases gradually with the increase in strain,and it decreases to about 0.8 at strain of 0.3.The EBSD microscopic analysis of the specimens at different deformation stages indicates that the variation of Taylor-Quinney coefficient is related to the twinning and microstructure evolution during the deformation process.