5E61铝合金板材折弯开裂原因分析

Study on cause analysis of bending crack of 5E61 aluminum alloy sheet

采用体视显微镜、扫描电子显微镜、金相显微镜对5E61-O铝合金板材的折弯开裂样品进行组织观察与分析。观察到折弯样品断口分为强剪切的裂纹起源区与传统的韧性断裂区两个部分;在样品中发现了粗大纤维晶、粗大AlTiEr化合物两种组织缺陷及其在断口中诱发的开裂、二次裂纹行为。该合金板材折弯开裂失效主要由大尺寸脆性化合物引发,需从成分设计和熔铸工艺角度入手,细化大尺寸化合物,改善折弯性能。

The fracture micromorphology of bending samples of 5E61 aluminum alloy sheet(O state) were investigated and analyzed by using the Stereomicroscope, scanning electron microscope, metallurgical microscope. Herein, it is found that the fracture area of the bending sample is categorized into two types, which are the shear crack origination zone and the traditional toughness fracture zone, respectively. Moreover, coarse fiber crystals and coarse AlTiEr precipitates are also found in the fracture samples, as well as which induce the cracking and secondary cracking behavior on the fracture surface. It means that the bending cracking failure is mainly caused by coarse brittle precipitates. For this reason, it is necessary to refine the size of coarse precipitates and improve the bending performance of sheet based on the composition design and casting process optimization.