Mechanical properties of friction welded joints of pure magnesium

Pure magnesium was friction welded using a brake type friction welding machine. Microstructures and mechanical properties of friction welded joints were investigated. The fine grain structure appeared near the weld interface, while a modified fiber structure is observed on the heat affected zone along the flow direction of burr. Hardness of the interface of the joint welded at friction pressure of 20 MPa was higher than that of the base metal, but joints welded at friction pressure of 30 and 40 MPa were nearly equal to that of the base metal. The tensile strength of welded joints increased with increasing both friction time and friction pressure, and the joint efficiency obtained about 87% of base metal. At friction pressure of 40 MPa, the joint shows elongation which is higher than that of the base metal. The joints welded at friction pressure of 20 MPa fractured at the weld interface, but the other joints fractured at the heat affected zone. The impact value of joints which are welded at friction pressure of 40 MPa and notched at the weld interface, is 1.8 times larger than that of the base metal.