Failure analysis of aluminum alloy swing arm welded joints
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Fracture failures in a welded motorcycle swing arm made of aluminum alloys 7075 and 7020 were studied by optical metallography and scanning electron microscopy (SEM). Lamellar tearing transverse to the loading direction of the swing arm was found in the collar structure. Analysis shows that during welding the collar piece close to the stringerlike inclusions led to tearing at the grain boundaries parallel to the rolling direction of the base metal. Subsequent cooling applied shrinkage stress to the stringers and opened the inclusion-matrix interfaces. These welding-generated tearing defects are the result of the material processing/welding operations and are transverse to the loading direction of the swing arm. Under workloads, these cracks propagated by fatigue, connected, and the swing arm fractured in a brittlelike mode.
KeywordsAL7075 aluminum alloy components for motorcycles fusion welded joints lamellar tearing
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