A356合金原位拉伸裂纹萌生与扩展行为分析

Analysis on Initiation and Propagation Behavior of In-situ Tensile Crack in A356 Alloy

采用扫描电镜原位拉伸观察了电解低钛A356合金铸态下裂纹萌生与扩展特征。结果表明:铸态A356合金裂纹优先萌生于二次枝晶臂间薄弱的共晶体区、大块的共晶硅相处;裂纹的扩展主要是微裂纹易沿着共晶体与基体界面扩展,合金组织中的共晶硅相对裂纹的扩展有一定的阻碍作用,当裂纹与共晶硅颗粒相遇时,扩展方向发生偏离而转向裂纹尖端前沿处有共晶体区开裂、共晶硅相发生断裂、或与基体界面发生分离的更薄弱区。

The fracture mechanism of A356 alloys as-cast was investigated. The crack initiation and propagation process were examined by in-situ tensile test using scanning electron microscope. The results show that crack initiates first in the lamellar eutectic area and block eutectic silicon phases. Crack propagates along the matrix/ silicon particle interface. The eutectic Si particles can block the propagation of crack. The crack paths deflect to the weaker area when encountering with Si particles.