Laser-TIG hybrid welding-brazing process of aluminum alloy/carbon steel and analysis of microstructures

A new method of laser-TIG hybrid welding-brazing of aluminum alloy/carbon steel was developed.The butt welding-brazing of aluminum alloy/carbon steel was realized, and the effects of welding parameters on joint characteristics were studied. Microstructures and mechanical properties of the joints were analyzed and tested by using scanning electron microscopy (SEM), energy dispersion spectrum (EDS) and electronic material testing machine. The results indicated that the maximum tensile strength of the joint reaches up to 83.6 MPa, the fracture occurred at the interface of steel/weld seam, the fracture model belongs to brittle fracture. The reaction layer hasheterogeneous thickness along steel/weld interface, its thickness is from 3 to 12 μm. The structures of the reaction layerare composed of η-Fe₂Al₅ close to steel side and τ5-Al_7.2Fe₂Si close to weld seam. The weld seam which is away from the interface layer consists of α-Al matrix and Al-Si eutectic phases.