Abstract: During the road test phase of the new energy sedan, the A380 die cast aluminum alloy hinge broke. Through various methods such as macroscopic observation, CT scanning, fracture analysis, metallographic examination, composition analysis, and mechanical performance testing, a systematic analysis was conducted on the cause of the failure of the connecting parts. Research has found that the failure mode of the connecting component is brittle intergranular fracture, with slight over heating characteristics including triangular grain boundaries, grain boundary widening, and grain boundary remelting, resulting in weakened grain boundaries. The tensile strength of the material is only 173MPa, far below the standard requirements.. Additionally, shrinkage porosity defects were present in the fracture area, acting as crack initiation sites under stress concentration. The failure mechanism is as follows: overheating during heat treatment led to grain boundary weakening; under external force, stress concentrated at subsurface shrinkage porosity defects, forming crack initiation sites; cracks propagated rapidly along the weakened grain boundaries, ultimately leading to the fracture of the component. The research results emphasize the critical impact of heat treatment process control on the performance of die-cast aluminum alloy components.