某变速箱A380铝合金悬置支架在整车生产线的螺栓安装时发生了开裂失效。通过宏观检查、化学成分分析、金相检验、断口分析、硬度和密度测试等对悬置支架开裂失效原因进行了分析；在不同工艺条件下进行了模拟，确定了造成开裂的工艺条件。结果表明：悬置支架在铸造过程中，由于脱模剂混入其内部形成大量铝的氧化物，该氧化物造成材料强度降低是引起悬置支架发生开裂的主要原因。该氧化物是在冷模状态下大量的脱模剂与快速压铸的铝液反应形成的铸造缺陷。

Cracking failure occurred in A380 aluminum alloy mounting bracket of a gearbox during bolt installation in the whole vehicle production line. The causes of cracking failure of mounting bracket were analyzed by macro examination, chemical composition analysis, metallographic examination, fracture analysis, hardness and density test. The simulation was carried out under different process conditions, and the process condition causing cracking were obtained. The results show that during the casting process, a large number of aluminum oxides formed in the mounting bracket due to the mixing of demoulding agent and the aluminum oxides, which resulted in the decrease of material strength, was the main cause of cracking of the mounting bracket. The oxide was a casting defect formed by the reaction of a large number of demoulding agents with liquid aluminum in rapid die casting under cold die condition.