In order to expand the market application range of friction stir lap welding in magnesium alloy dissimilar materials

AZ31 magnesium alloy and LA141 magnesium lithium alloy were welded by friction stir lap welding. The microstructure

microhardness and shear tensile of friction stir lap welded joints were analyzed and tested by means of optical microscope

Vickers hardness tester and universal testing machine. The results show that when the rotation speed is 1800 r/min and the welding speed is between 80 mm/min and 120 mm/min

the friction stir lap welding of AZ31/LA141 had sound joints without obvious defects. Under the same welding process parameters

the grain size of the upper layer AZ31 and the lower layer LA141 in the thermo-mechanically affected zone on the advancing side are both smaller than those of the thermo-mechanically affected zone on the retreating side

while the grain size of the heat affected zone on the advancing side are larger than the grain size of the heat affected zone on the retreating side. When the welding speed increases

the grain size of the thermo-mechanically affected zone on the advancing side of the upper layer AZ31 and the lower layer LA141 decreases accordingly. The microhardness values of the upper AZ31 and lower LA141 weld nuggets have different trends. The former increases first and then decreases

while the latter tends to increase. With the increase of welding speed

the tensile shear force of AZ31/LA141 lap joint increases first and then decreases.