The cracks near 5A06 aluminum alloy welding joint are analyzed. The metallurgical structure of base metal, welding joint and heat-affected zone are analyzed and the results indicate that organization is uneven and there is inclusion in the aluminum alloy, the precipitates are found in grain inner and boundary. The crack propagation character are analyzed and the results indicate that the crack originates from the inclusion of the specimen edge, and crack propagation along the grain boundary. Micro-fracture and macro fracture are analyzed by SEM and found that there are secondary cracks in the fracture, and the fracture was brittle fracture.%针对5A06铝合金焊缝附近出现的裂纹进行了分析.5A06铝合金母材、焊缝及热影响区组织分析结果表明,材料成型后的组织不均匀,并且存在夹杂物,晶内和晶界有析出相出现.采用光学显微镜对裂纹的扩展特征进行分析,结果表明,裂纹在材料边缘夹杂物处启裂,以沿晶的特征进行扩展.采用SEM对断口进行微观和宏观分析,断口中存在二次裂纹,断口为脆性断裂.
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