Microstructures and mechanical properties of AZ91 magnesium alloy castings joint by friction stir welding

Abstract

AZ91 magnesium alloy castings plate with 5 mm thickness was friction stir welded. The microstructures and mechanical properties of FSW joints were investigated. Regardless of the welding conditions, the microstructures of stirred zone showed finer than that of the base metal. Tensile strength of all the joints showed higher value than that of the base metal. The tensile strength and elongation of joints showed as same as base metals. All the tensile tested joints were fractured at the base metal. Regardless of the welding conditions, the impact value of joints showed higher value than that of the base metal, and the maximum impact value of joint was 295% of the base metal. The highest temperature of the friction stir welding process showed 669 K, and it decreased with increasing welding speed. The welding force increased with increasing welding speed, and decreased with increasing rotational speed of tool.