Heterogeneity of mechanical properties of friction stir welded joints of 1050-H24 aluminum alloy

摘要

Many studies on the microstructural characteristics and mechanical properties of joints have indicated that a softened region occurs in the friction stir welded joints of heat-treatable aluminum alloys [1-5] and strainhardened aluminum alloys [6-10]. In order to solve the joint softening problems of heat-treatable aluminum alloys, some researchers adopted postweld aging treatment techniques and obtained better compensating results [1-3]. Up to now, however, no better method has been found to improve the deterioration in mechanical properties of friction stir welded joints of the strainhardened aluminum alloys. In principle, any joint can be considered to be composed of finite thin-layers in the direction of thickness, and any thin-layer is different from the other ones in mechanical properties because they experience different thermo-mechanical actions during friction stir welding (FSW). If the mechanical properties of some weak thin-layers of the joint can be improved, the mechanical properties of the entire joint will be raised. However, the real difference in mechanical properties between thinner-layers is still unknown. This letter aims to demonstrate this difference so as to obtain useful information for improving the mechanical properties of the joints of strain-hardened aluminum alloys.