Zhang Bin, Wang Jin, Wang Yang, Wang Yu, Li Ziran
CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China.
Materials (Basel). 2019 Feb 22;12(4):659. doi: 10.3390/ma12040659.
This study is an experimental investigation on the tensile responses of Ti⁻5Al⁻2.5Sn alloy over a wide range of strain rates. Uniaxial tension tests within the rate range of 10⁻10¹ s are performed using a hydraulic driven MTS810 machine and a moderate strain-rate testing system. The high-rate uniaxial tension and tension recovery tests are conducted using a split-Hopkinson tension bar to obtain the adiabatic and isothermal stress⁻strain responses of the alloy under dynamic loading conditions. The experimental results show that the value of the initial yield stress increases with the increasing strain rate, while the strain rate sensitivity is greater at high strain rates. The isothermal strain-hardening behavior changes little with the strain rate, and the adiabatic temperature rise is the main reason for the reduction of the strain-hardening rate during high strain-rate tension. The electron backscatter diffraction (EBSD) analysis of the post-deformed samples indicates that there are deformation twins under quasi-static and high-rate tensile loadings. Scanning electron microscope (SEM) micrographs of the fracture surfaces of the post-deformed samples show dimple-like features. The Zerilli⁻Armstrong model is modified to incorporate the thermal-softening effect of the adiabatic temperature rise at high strain rates and describe the tension responses of Ti⁻5Al⁻2.5Sn alloy over strain rates from quasi-static to 1050 s.
本研究是对Ti⁻5Al⁻2.5Sn合金在宽应变率范围内拉伸响应的实验研究。在10⁻10¹ s的速率范围内，使用液压驱动的MTS810机器和中应变率测试系统进行单轴拉伸试验。采用分离式霍普金森拉杆进行高应变率单轴拉伸和拉伸恢复试验，以获得合金在动态加载条件下的绝热和等温应力⁻应变响应。实验结果表明，初始屈服应力值随应变率的增加而增大，且在高应变率下应变率敏感性更大。等温应变硬化行为随应变率变化不大，绝热温升是高应变率拉伸过程中应变硬化率降低的主要原因。对变形后样品的电子背散射衍射（EBSD）分析表明，在准静态和高应变率拉伸载荷下存在变形孪晶。变形后样品断口的扫描电子显微镜（SEM）照片显示出韧窝状特征。对Zerilli⁻Armstrong模型进行了修正，以纳入高应变率下绝热温升的热软化效应，并描述Ti⁻5Al⁻2.5Sn合金在从准静态到1050 s应变率范围内的拉伸响应。
