高应变速率下两种损伤容限型钛合金的动态压缩变形行为

摘要

Dynamic compression experiments on the two damage tolerance titanium alloys of TC4-DT and TC21 were carried out at strain rates from 1 000 s-1 to 8 000 s-1 by the split Hopkinson pressure bar method respectively,and then the fracture morphology and microstructures were investigated by scanning electron microscopy and optical microscopy.The results show that the two titanium alloys have exhibited a strengthening and plasticity-increasing effect induced by strain rates,and the flow stresses of TC21 titanium alloy were higher than those of TC4-DT titanium alloy at the same strain rate.The two titanium alloys both showed a shear failure characterized by the alternative distribution of dimple area and smooth area at the fracture surface.At the same strain rate,the number of dimples in TC4-DT titanium alloy was more and the elongation was greater than those in TC21 titanium alloy.The adiabatic shear bands were not observed in TC21 titanium alloy but observed clearly in TC4-DT titanium alloy.With the increase of strain rates,the width of the adiabatic shear bands increased,and accompanied by the crack initiation,propagation and polymerization along the direction of the adiabatic shear bands.%采用分离式霍普金森压杆(SHPB)装置在1000~8000 s－1应变速率范围内分别对TC4-DT 和 TC21两种损伤容限型钛合金进行了动态压缩试验，并利用扫描电子显微镜和光学显微镜观察了其断口形貌和显微组织。结果表明：两种钛合金都表现出一定的应变速率增强、增塑效应，在相同应变速率下 TC21钛合金的流变应力要比 TC4-DT 钛合金的大；两种钛合金均表现为剪切破坏，断口上均交替分布着韧窝区和平滑区，与 TC21钛合金相比，在相同的应变速率下 TC4-DT 钛合金的韧窝数量更多，延伸得更长；TC21钛合金中没有明显的绝热剪切带，而 TC4-DT 钛合金中有明显的绝热剪切带，其宽度随应变速率的增加而增大，同时沿剪切带方向还伴随着裂纹的萌生、扩展和聚合。