Study on mechanical properties and microstructure analysis of welded joints of 7A05 aluminum alloy by laser-MIG hybrid welding

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Статья. Опубликована в рамках конференции "2nd International Conference on Electronic & Mechanical Engineering and Information Technology" — 2012. — С. 1465-1470.7A05 aluminum alloy joints were fabricated by Laser-MIG hybrid welding, of which the tensile strength was tested at room temperature. The tensile fracture surfaces and microstructure were analyzed by SEM and TEM. The fracture surface analysis showed fracture morphologies of small dimple of 2 ~ 5μm on the heat affected zone (HAZ) and big dimple of 30 ~ 50μm on the weld bead. The fracture is inter-granular fracture with a small amount of cleavage fracture. TEM analysis showed that the HAZ region didn't exists η'-phase, but Al3Zr, i.e., during welding thermal cycle, the joints appeared obvious η'-phase back dissolved so that lost η'-phase dispersion strengthening effect. O, Na and Fe impurities were detected in the joint, of which the crack originated during tensile testing. Both the impurities and η'-phase back dissolved are responsible for the degrading of the welded joints mechanical properties.IntroductionExperimentExperimental results and analysisTensile mechanical properties at room temperatureThe hardness distribution of the welded jointsFracture surface analysisMicrostructure transformation of the welding jointMicrostructure of HAZMicrostructure of the weld beadConclusionsReferences