Microstructures and Mechanical Properties of MIG Welding Joint of 7005 Aluminum Alloy

摘要

Metal inert-gas welding of 7005 aluminum alloy profiles was conducted using ER5356 filler wire. The mechanical properties and microstructures of the welding joint were investigated by OM, SEM, micro-hardness test and tensile test. The results show that the tensile strength, yield strength, and elongation of the welding joint are 288 MPa, 190 MPa and 3.9%, respectively. The weld zone is characterized by cast structure. The tensile fracture morphology of the welding joint is characterized by ductile rupture. The welded grain near the fusion line is columnar crystals along the radiation direction and the grain in the fusion area is coarse. The fibrous microstructure is found in the base metal, while in the heat affected zone, the recrystallization occurs. The soften zone in the heat affected zone (HAZ), forms due to the coarsening of precipitate phase Mg_2Si. The longer the natural aging time, the greater micro-hardness.