Analysis on Fracture Reasons of Automobile Steering Wheel Frames

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.