Microstructural and electrochemical characterization of Aluminum / Steel Joints Conducted by Dual-Beam Laser

The microstructure, mechanical and electrochemical properties of dissimilar materials welded joints, which conducted by laser dual-beam, composed of dual-phase stainless steel DP 780 and 5083 aluminum alloy has been investigated. Microstructures of the joints were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Properties of the joints were evaluated by performing micro-hardness tests and electrochemical tests. The results show that the microstructure of weld is consists of three parts, the zone of coarse-grained martensite, the lath martensite zone and the fine-grain martensite zone from bottom to top. The inter-metallic compound FeAl2 is distributed on the edge of the weld on steel-side, while the inter-metallic compound Al3Fe exists as discrete island on aluminum-side. After remelting and recrystallizing, the heat-affected zone micro-hardness of dual-phase stainless steel is harder than that of base material and the weld, while the area with highest micro-hardness of aluminum is the weld. The electrochemical characterization is acquired by the scanning vibrating electrode technique (SVET), the peaks of anodic current density are near to fusion zone, but the peaks of cathode current density are distribute in weld and HAZ on the SVET maps. The corrosion resistance of the aluminum alloy base material and the lower part of weld is better than other areas after prolonged corrosion.