Microstructures and mechanical properties of friction stir spot brazed joint of AZ31 magnesium alloy

The effects of several solders and hard phases（ zinc solder,tin solder,and Si C hard phase particles） on microstructure,ultimate tensile shear load,and hardness distribution of magnesium alloy friction stir welded joints were investigated. The results showed that when zinc solder was added,the solder would react completely with the base metal to form hard phase of MgZn₂. The hard phase of the weld nugget zone hinders the plastic flow of the metal. And a larger brazing interface will be formed in the brazing area. The ultimate tensile shear load of the welded joint was increased from 3. 5 kN to 5. 8 kN. The joint also had a high hardness.