采用体视检测、显微组织观察和硬度测试等分析方法,对汽车后桥半轴早期失效原因进行分析。结果表明,材料失效的主要原因是前期调质处理时由于过热导致心部组织粗大,且表面感应淬火层组织粗大,淬硬层偏深,严重降低材料的强度与韧性。同时断口附近组织中的大块非金属夹杂也是导致材料应力集中形成裂纹的原因之一。 The causes of the early failure of the semi axle of the rear axle of the automobile were analyzed by the methods of stereo vision examination, microstructure observation and hardness test. The results show that the main reason of material failure is that the core tissue is coarse due to overheating in the early stage of quenching and tempering, and the surface induction quenched layer is coarse and the hardened layer is deep, which seriously reduces the strength and toughness of the material. At the same time, the large non-metallic inclusions in the tissues near the fracture are also one of the reasons leading to the stress cracking in the material.