The Study Of Friction Stir Spot Weld Of Dissimilar Material Of Aluminum Alloy And Magnesium Alloy

Lightweight materials of aluminum(Al)alloys and magnesium(Mg)alloys are becoming much more widely used due to the increasing demands for energy saving and material recyclability in automotive industry.But traditional fusion welding of Al and Mg alloys will produce massive brittle intermetallic compounds(IMCs)which is detrimental to the mechanical properties.And other methods of joining also have disadvantages.In this study,we choose the Al alloy 6061 and Mg alloy ZN30 K as the material.We try 18 different parameters for the process of FSSW which are carried out by pin-less tool.And the microstructure and mechanical properties are studied.The results indicate that all the weld joint are beautiful without keyhole.The macrostructure is symmetrical because of the stir of the tool.There appears microvoids at the rotation speed of 600 rpm and cracks come into being at the rotation speed of 2100 rpm.Fine grains are produced in the SZ because of the recrystallization.The grains are elongated in the TMAZ as the result of the stir of the tool.The study of the material flow in the process are complicated.The process maybe are as follows: the material is squeezed into the groove at the process of the plunge into material of the tool and flow to the two sides as the tool retrieve.The study of the microhardness indicates that with the increase of the rotation speed,the microhardness' distribution is more equal.Some value is higher than the others as the consequence of the presence of the IMCs.As for the tensile-shear failure load,the joint welded by the plunge depth D 1?D 2? D 3 of 0.3 mm?0.5 mm?0.7 mm and rotation speed of 1800 rpm is the highest.By the study of the fracture of the joint,the failure occurs at the interface of the intermetallic layer.