多晶纯钛中应变率拉伸力学行为实验研究

Experimental study of tensile property of cp-Ti at intermediate strain rates

利用MTS809和自行研制的中应变率材料试验机，在室温下对多晶纯钛进行了0．004-14^s-1叫的准静态至中应变率范围内的拉伸试验，得到了多晶纯钛的拉伸应力应变关系．试验结果表明，多晶纯钛的拉伸力学行为在准静态至中应变率范围内具有明显的应变率强化效应和应变硬化效应，且有随应变率增大而逐渐明显的绝热温升软化效应．金相观察显示，拉伸变形过程中伴随孪生机制且孪晶密度随加载应变率的升高而增大．基于Johnson-Cook模型，提出了通过引入综合绝热温升软化系数哆来计及与应变率相关的绝热温升软化效应的修正的热粘塑性本构模型．结果表明，该模型能较好地表征多晶纯钛在本试验应变率范围内的拉伸力学行为．

The tensile behavior of cp-Ti at room temperature was investigated at the strain-rate range ot 0. 004- 14 s^-1 using MTS809 and self-designed intermediate material testing apparatus. Experimental results indicate that the tensile property of cp-Ti at intermediate strain rates has significant strain rate strengthening, strain hardening and strain rates sensitive thermal-softening. At the microscopic level, deformation twinning was observed. The deformation twinning density increases with increasing strain rates. Based on Johnson-Cook model, a thermo-viscoplastic constructive model considering strain rates sensitive thermal-softening was used to describe the tensile stress-strain relationship of cp-Ti at the tested strain rates. The simulation results are in good agreement with the experimental ones.