一种典型近α型钛合金绝热剪切带组织特征研究

Microstructure characteristics of adiabatic shear band in a typical near α-type Ti alloy

摘要:

本文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开展了研究,结果表明：合金的动态应力应变曲线呈现典型的三阶段特征,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30μm以内。

Abstract:

The adiabatic shear characteristics of a typical near α-type Ti-6Al-2Zr-1Mo-1V Ti alloy at different strain rates have been investigated by hat shaped specimen. The results show that the dynamic stress-strain curve can be divided into three typical stages, which correspond to strain hardening, heat softening and shear localization, respectively, and finally develops into mature ASB；Close to the shear band，the primary α and second α distorted or even fractured in the transition zone，and showing the characteristics of twin deformation；In the near shear zone, the Kernel average misorientation(KAM) increases, α phase which is favorable to dislocation slip/twin orientation has a preferential plastic deformation, forming substructure, grain fragmentation and dynamic recrystallization. With the increase of strain rate, the width of shear band extended, and the vortex structure is supplemented by 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 this alloy is a softening band, and the width of the heat-affected zone is about 30μm around ASB.