Data base of impact stress-strain relations of high strength titanium alloys

高强度β钛合金（Ti-15V-3Cr-3Sn-3Al）在高应变速率下的应力-应变关系是本研究的重点，并从时效条件、温度和应变速率等方面进行了系统的研究，构建了相关的数据库，因为该材料在未来的高速运输车辆中具有广阔的应用前景。为明确宽应变范围内应力应变关系的温度依赖性和应变速率依赖性，首先对未时效和时效材料进行了准静态压缩试验、应变速率变化试验和冲击试验。由于温度和应变率对强度的影响与热激活变形过程有关，我们可以应用这一概念来预测高应变率下的应力应变关系，并考虑变形过程中的绝热加热效应。实验结果很好理解。采用新研制的分离式霍普金森杆式冲击试验装置，获得了三种以上的时效硬化试样的冲击拉伸应力-应变关系。除了材料的冲击强度数据库外，还总结了以下内容。(1)拉伸和压缩试验中的冲击强度均高于静态值，与温度和时效处理无关，但在极低温度下弹性变形范围内发生脆性断裂的情况除外。(2)较低温度下的冲击应力-应变关系中，工件软化现象更为明显。(3)冲击试验伸长率和收缩率均增加，与温度和时效条件无关。(4)流变应力对温度和应变速率的依赖关系几乎与时效处理无关，因此，只有将应力的非热分量转化为应变关系，才能唯一地预测冲击应力-应变关系，并在适当的高温下进行静态试验。少

The stress-strain relations of high strength beta titanium alloy(Ti-15V-3Cr-3Sn-3Al) at high strain rate are focused in the present study, and are systematically investigated to frame the relevant data base in terms of the aging conditions, temperature, and strain rate, since the material is very promising for high velocity transportation vehicles in near future.To clarify the temperature and strain rate dependence of stress-strain relations in the wide strain range, the quasi-static compression test, the strain rate change test, and the impact test were first carried out for the un-aged and the aged materials. Since the temperature and strain rate effect on the strength is well understood in connection with the thermally activated deformation process, we can apply the concept to predict the stress strain relation at high strain rate by taking account of adiabatic heating effect during deformation. The experimental results were well understood. Impact tensile stress-strain relations fo … More r three kinds of age-hardened specimens were fully obtained using a newly developed split Hopkinson bar type impact testing apparatus. Besides the data base for impact strength of the materials, followings are also summarized. (1)Impact strength both in the tension and the compression test was always higher than the static value independent of temperature and aging treatments, except the case of the brittle fracture occurred in the elastic deformation range at very low temperatures. (2) Work softening phenomenon was observed much more significantly on the impact stress-strain relations at lower temperatures. (3) The elongation and the reduction of area both increased in the impact test independent of temperature and aging conditions. (4) Temperature and strain rate dependence of the flow stress was almost independent of aging treatment, and consequently, the impact stress-strain relations can be uniquely predicted only depending the athermal component of stress to the strain relation which would be respectively evaluated in the static test at appropriately high temperatures. Less