Investigation on Microstructure and Mechanical Property of the A7N01 Aluminum Alloy Welding Joint

The A7N01 aluminum alloy was welded by MIG welding in test, and the microstructure and mechanical property of joint were investigated. The results of experimentation show that the feature of the A7N01 aluminum alloy MIG welding joint is perfect with a gentle transition. The microstructure of fusion metal in A7N01 joint is as-cast grain. The microstructure of fusion zone consists of the fine columnar grains. It is rolling structure in the parent metal. In HAZ, the rolling structure is disappearing. The eta' (MgZn2) strengthening phases were precipitated in the grain boundary of the A7N01 aluminum alloy. The size of eta' strengthening phase is about 5-10 nm. There is no precipitation phase in welding metal of A7N01 joint. The fine eta' transitional phases of the primeval parent metal are turned to the coarse eta (MgZn2) stable phases of the HAZ. The size of eta strengthening phase is about 50 nm. The tensile strength and the percentage elongation after fracture of A7N01 welding joint is below the parent metal.