Effects of pin diameter on microstructures and mechanical properties of friction stir spot welded AZ31B magnesium alloy joints

摘要

The effects of pin diameter on the microstructure and mechanical properties of friction stir spotnwelded AZ31B magnesium alloy joints were investigated using microstructural observations,ntensile tests and microhardness tests. The results showed that with an increase in the pinndiameter, the height and width of the curved interface in the friction stir spot welded AZ31Bnmagnesium alloy joints increased because of the strong effect of stirring and high temperaturenobtained when large sized pins were adopted. An increase in the pin diameter led to thencoarsening of a-Mg grains in the stir zone, thermomechanical affected zone and heat affectednzone because of heat generation, resulting in the decrease in microhardness of stir zone,nthermomechanical affected zone and heat affected zone. The tensile shear force of the friction stirnspot welded AZ31B magnesium alloy joints increased with the increase in pin diameter becausenthe height and width of the curved interface dominated the failure of the specimens.