AZ31镁合金中绝热剪切带的组织演变规律

Microstructure Evolution of Adiabatic Shear Bands in AZ31 Magnesium Alloy

摘要:

为了深入了解镁合金绝热剪切带与裂纹的关系，进而揭示镁合金在高速冲击载荷作用下局部变形绝热剪切的组织演变规律，采用分离式Hopkinson压杆对AZ31 镁合金的帽状式样进行冲击压缩实验，而后利用光学显微镜，扫描电镜和维氏硬度计分别对冲击后的AZ31试样进行分析。结果表明，绝热剪切带形成于最大剪应力方向，随着冲击载荷的不断增加，沿着切应力方向上的微孔洞和微裂纹不断长大，直至彼此相互连接成裂纹，最终导致材料的断裂。经对剪切带及周围组织维氏硬度的测量发现，剪切带内细小晶粒区的硬度明显高于周围组织。

Abstract:

In order to have a deep understanding of the relationship between adiabatic shear bands and cracks in magnesium alloys, the split Hopkinson pressure bar (SHPB) was used to study the deformation localization of the hat-shaped AZ31 magnesium alloy specimen under high strain rate impacting. The microstructure and the cracking formed within the adiabatic shear band were observed by OM and SEM, and the microhardness within and around the adiabatic shear band were tested. The results demonstrate that the adiabatic shear band is formed along the maximum shear stress direction. With the increasing of the impact loading, the micro holes form along the adiabatic shear band. When the micro holes are coarsened and connect with each other the crack forms and then the specimen is broken. The micro hardness of the microstructure in the core of the adiabatic shear band is higher than that of the microstructure around the adiabatic shear band.