Study On Welding And Post Welding Heat Treatment Of211Z Aluminium Alloy

211Z aluminium alloy is a kind of cast aluminium alloy which is developedrecently in China. Because of its outstanding mechanical properties and economicalefficiency, it has been applied in many fields e.g. aviation, aerospace. In order tobroaden its application, the welding propertities of211Z aluminium alloy areinvestigated.211Z aluminiun alloy sheets are welded through changing three basicparameters, i.e., the weld methods, welding parameters and the welding rods. Themain contents includes: the forming characteristics and defects of211Z aluminiumalloy welded joints; an analysis of microstructure changes of the211Z aluminiumalloy welded joints using optical microscope, scanning electron microscope andtransmission electron microscope; a study of the mechanical properties andhardness of the211Z aluminium alloy welded joints; the welding technologicalparameters’ influence on joints microstructure and mechanical properties arediscussed; post welding heat treaments are set according to different welding rods,providing theoretical basis for engineering application.Evaluations are taken on the forming characteristics and defects. It shows that,both TIG and MIG welding can guarantee the211Z aluminum alloy plates’connection without obvious crack or porosity.Analyses of microstructure are taken on three state of211Z aluminiun alloywelding jonts. It shows that weld zone and heat affected zone are the weak zones ataging sheet joins and the central region of the weld echibits a trough in the hardnesstrace. Grains in HAZ are much bigger compared with parent metal. The weldingheat contributes to the second phase precipitation at the cast sheet joins, andsamples failure at base metal other than the joins.The strength of the samples taken from TIG is more stable and higher than thatfrom MIG, so is the elongation. Joints welded by cast sheets and Al-Mg rod, WZ isfilled with equiaxial grains at TIG joints, dendrite grains at MIG joints. Porositiestend to occur at TIG joins.Four welding rods are chosen for experiment. The mechanical property ofAl-Mg joint is better than the other two. Al-Mg, Al-Cu and Al-Si joint is filled withequiaxed grains, dendrite grains and columnar dendrite grains, respectively. Withthe adding of the Si content and welding heat input, the content of columnar dendrite grain tends to increase.After the solution and aging treament, the tensile strengths of Al-Cu and Al-Sijoints are412MPa and372MPa, yield strength for358MPa and239MPa, elongationratio for3.5％and5.5％, respectively.