Tensile Properties of Friction Stir Welded Joints of 7050 Aluminum Alloy Before and After Heat Treatment

摘要

In this study, the mechanical properties of defect-free friction stir welded 7050-T7451 joints with different heat input was investigated. Various heating rate solution heat treatment and aging treatment were given to the joints. The results show that the heat affected zone is weak zone for as-welded joints. The lower the minimum-hardness is in the heat affected zone, the lower the tensile strength of the welded joints is. The softening was removed in the heat affected zone after the solution heat treatment and aging treatment. The tensile strength is improved significantly for the low heat input joint. While joints are produced with higher heat input, the grain structure is instability in the nugget zone during the solution heat treatment. Especially, the strengthening function of the solution heat treatment and aging treatment is fail while the millimeter scale grain were formed in the nugget zone.