Study on the effect of nano SiC on the properties of friction stir welded joints of magnesium alloy

In order to improve the comprehensive performance of AZ31 magnesium alloy welded joints, the friction stir welded joints without nano-SiC-1 pass and with nano-SiC-1 pass and 4 passes were studied respectively. The microstructure and mechanical properties of the welded joints were analyzed by optical microscope, microhardness tester and tensile testing machine. The corrosion behavior of the joints was studied by electrochemical workstation. The corrosion morphology, element composition and phase composition of the joints were analyzed by scanning electron microscopy, EDS and XRD. The results show that the friction stir welding joint is well formed and has no defects. The microstructure of the weld nugget zone of the joint is uniform equiaxed grains. The increase of welding passes can effectively improve the distribution of SiC particles. The existence of heterogeneous nucleation sites plays a role in grain refinement and improves the mechanical properties of the joint. In the 3.5% NaCl solution corrosion test, the corrosion resistance of the joint containing SiC particles is improved, and the corrosion resistance of the SiC-4 pass joint is the best.