高速弹丸冲击诱发TC32钛合金中绝热剪切带的组织演化行为

Microstructural evolution behavior of adiabatic shear bands induced by high-speed projectile impact in TC32 titanium alloy

摘要:

采用光学显微镜(OM),扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究了Ti-5Al-3Mo-3Cr-1Zr钛合金在高速弹丸冲击后的组织特征和演变行为。在弹坑周围,绝热剪切带(ASB)和剪切应力一直呈半圆状分布。观察到绝热剪切带中尺寸较大等轴晶粒和细长板条亚晶粒的旋转细化过程。采用聚焦离子束(FIB)技术准确地从ASB中的裂纹尖端取样制备TEM样品,在裂纹尖端区域周围发现非晶区、非晶-纳米晶过渡区域、细小纳米晶区共存。计算结果表明,绝热剪切带内温度升高可导致微观组织熔化,快速淬火后形成非晶区和细小的纳米晶。由于绝热剪切带中的显微组织是细小的等轴晶和非晶,具有较高的强度,使形变带与基体之间成为相对较弱的区域,绝热剪切带中的裂纹也主要在该区域萌生,裂纹通过微孔洞旋转联结的方式扩展。

Abstract:

The microstructure characterization and evolution behavior of TC32 titanium alloy after high-speed projectile impact were studied by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The distribution of adiabatic shear band(ASB) and stress around the crater has always been a semi-circular diffusion. The rotating refinement process of large equiaxed grains and elongated lath subgrains in adiabatic shear band was observed. Focus ion beam (FIB) technology was used to accurately prepare TEM samples from the crack tip in the ASB. It was found that the coexistence of the amorphous regions, the amorphous-to-crystalline transition regions, the fine-scale nano-crystalline region around the crack tip. The calculation proved that the temperature rise in ASB could cause microstructure melting, the amorphous regions and small size nanocrystals were formed after fast quenching. Because the microstructure in the ASBs is fine equiaxed grains and amorphous with higher strength, the area between the deformed band and matrix is relatively weakened, and it is found that the initiation of cracks in adiabatic shear bands is mainly concentrated at the junction of deformed band and matrix, and the crack propagate in the form of microvoids rotation coupling.