Influence of Microstructure of Friction Stir Welding Joint on Growth of Microarc Oxidation Coating on 2219 Aluminum Alloy

A ceramic coating of 50 μm thick on the surface of friction stir welding (FSW) joint on 2219 aluminum alloy was fabricated by microarc oxidation (MAO) technique in the silicate electrolyte. The surface morphology, phase constituent and microhardness of the coatings on the parent phase and FSW joint of aluminum alloy were investigated, furthermore the interactions of alloy microstructure and MAO coating growth were analyzed. The results show that the effect of microstructure of aluminum alloy on growth of MAO coating is weak, and the properties of MAO coatings on the parent phase and FSW joint of aluminum alloy are almost same. The ceramic coatings at different zones of joint consist of α―Al2O3, γ―Al2O3 and mullite (3Al2O3·2SiO2) phases. The microhardness of coatings on the parent phase and FSW joint of aluminum alloy is same, which average microhardness is about HV 1500. In addition, the microstructure of aluminum alloy near the coating/alloy interface is not influenced by high―temperature process of microarc discharge.