【摘要】 采用帽形试样,对一种典型近α型Ti-6Al-2Zr-1Mo-1V钛合金在不同应变率条件下的绝热剪切特征进行了研究。结果表明:合金的动态真应力-应变曲线呈现典型的3阶段特征,分别对应于应变硬化、热软化和剪切局部化阶段,最终形成绝热剪切带(ASB)。在近剪切带处,初生α相和次生α相在过渡区内发生扭曲变形,甚至断裂,出现孪晶变形特征。近剪切带区域由于微观取向差增大,利于位错滑移/孪晶取向的α相优先发生塑性变形,形成亚结构,晶粒碎化,发生动态再结晶;随着应变率的提高,剪切带宽度呈增大趋势,且出现旋涡结构以协调和适应变形;通过纳米压痕试验,分析了 ASB及其附近与基体的α相、β相的弹性模量和显微硬度,表明该合金的绝热剪切带为一条软化带,影响区的宽度在ASB附近30 μm以内。更多还原

【Abstract】 The adiabatic shear characteristics of a typical near a-type Ti-6 Al-2 Zr-1 Mo-1 V alloy at different strain rates were investigated by hat-shaped specimen.The results show that the dynamic true stress-strain curve of the alloy can be divided into three typical stages,which correspond to strain hardening,hot softening and shear localization,and finally develops into mature adiabatic shear band(ASB).Close to the shear band,the primary α and secondary α distort or even fracture in the transition zone,showing the characteristics of twin deformation.In the near shear band zone,the Kernel average misorientation(KAM) increases,and a phase which is favorable to dislocation slip/twin orientation occurs a preferential plastic deformation,forming substructure,grain fragmentation and dynamic recrystallization.With the increase of strain rate,the width of shear band extends,and the vortex structure appears conductive to the coordination and adaptive deformation.The elastic modulus and microhardness of α-phase and β-phase of ASB,near ASB and matrix were analyzed by nano indentation test.The results show that the adiabatic shear band of the alloy is a softening band,and the width of the heat-affected zone is about 30 μm around ASB.更多还原