U-5.7Nb合金动载下绝热剪切带的形成及其演化机制

Formation and Evolution Mechanism of Adiabatic Shear Bands in U-5.7Nb Alloy Subjected to Dynamic Loading

研究了U-5.7Nb合金在应变速率为8000s^(-1)下绝热剪切带的形成及其演化机制。通过控制应变速率,采用应变限位环的方法实现了U-5.7Nb合金在不同应变下的动态变形。结果表明:随着应变的增加,U-5.7Nb合金动载下会形成两种类型的绝热剪切带:形变带和转变带。形变带形成所需的临界应变值接近于0.33,而转变带形成所需的临界应变值接近于0.39。显微组织观察表明形变带内部由严重拉长的畸变组织组成,而转变带内部主要由细小等轴的晶粒组成。基于不同应变下绝热剪切带的表征,预测了U-5.7Nb合金动载下塑性变形及其断裂过程。

The formation and evolution of adiabatic shear bands in U-5.7Nb alloy deformed at a strain rate of 8000 s-1 were investigated. Dynamic deformation at different strains of U-5.7Nb alloy was obtained by the strain stopping rings and the controlled strain rate. The results show that with the strain increasing, two types of adiabatic shear bands including deformed band and transformed band are distinguished in U-5.7Nb alloy under the dynamic deformation. The critical strain value for the deformed band formation approaches to 0.33, and that for the transformed band formation is close to 0.39. Microscopic observation shows that the deformed bands are composed of severely elongated distortional characterization of adiabatic shear dynamic loading were speculated. structure while the transformed bands are mainly composed of ultrafine equiaxed grains. Based on bands at different strains, the plastic deformation and fracture process of U-5.7Nb alloy subjected to dynamic loading were speculated.