Method for preventing abnormal grains of aluminium alloy friction stir welding connector from growing

The invention discloses a method for preventing abnormal grains of an aluminium alloy friction stir welding connector from growing. The method comprises the steps of S1, polishing and cleaning the surface of a to-be-welded aluminium alloy workpiece; S2, fixing the treated to-be-welded aluminium alloy workpiece to a friction stir welding machine tool, and carrying out friction stir welding to obtain an FSW aluminium alloy workpiece; S3, putting the FSW aluminium alloy workpiece obtained in the S2 into a thermal treatment furnace, heating the FSW aluminium alloy workpiece to 300 DEG C to 500 DEG C, keeping the temperature for 48 to 72 h, carrying out furnace cooling to a certain temperature, taking out the workpiece, carrying out air cooling, and carrying out recrystallization annealing treatment; S4, carrying out solution treatment on the FSW aluminium alloy workpiece treated in the S3; and S5, carrying out manual aging treatment on the FSW aluminium alloy workpiece treated in the S4. According to the treated aluminium alloy friction stir welding connector, the growing of abnormal grains of which the area fraction is larger than 90% can be decreased, and the strength requirement can be met.