某些镁合金方向盘骨架在车辆试验过程中发生断裂，通过宏观观察、扫描电镜及能谱分析、金相检验等方法，分析了方向盘的断口形貌及组织特征，以确定方向盘断裂的原因。结果表明：断裂方向盘经历了微裂纹形成与扩展和快速断裂两个阶段；断裂方向盘组织中晶粒尺寸不均匀，存在大枝晶和缺陷，而未断裂方向盘组织中的晶粒相对细小致密，这些是方向盘骨架断裂的主要原因。

Some steering wheel frames of magnesium alloy fractured during vehicle tests. The fracture morphology and structure characteristic of the steering wheels were analyzed to reveal the fracture reasons by using macroscopic observation, scanning electron microscopy and energy spectrum analysis, metallographic exanimation and so on. The results show that:the fractured steering wheels experienced two processes of formation and propagation of microcracks and fast fracture; the grain size in the structure of the fractured steering wheels was nonuniform, and bulky dendritic crystal and defects existed in the structure, while the grains in the structure of the intact steering wheel were fine and compact, which were the main reason of the fracture of the steering wheels.