Study On Microstructure And Properties Of Friction Stir Welding For Mg/Al Dissimilar Alloys By Interface Alloying

As the lightest and the most economical metal structural material,magnesium alloys have many advantages such as high specific strength stiffness,and good processing properties,so they are entitled as the green engineering material for the 21 st century.In order to extend the application of magnesium alloys,the sound bonding is of great importance,especially bonding with aluminum alloys,which makes the structure reduce the further weight and shows the advantages of two metals.It has a broad application prospects in the fields of aerospace and automotive industry.However the brittle Mg/Al intermetallic compounds can be easily found in the Mg/Al joints,which will deteriorate the performance of joints.In this paper,AZ31 magnesium alloy and 5052 aluminum alloy were used as the research object,and the alloy of Mg/Al dissimilar alloy was studied by Cu alloying method.The welds microstructure and mechanical properties of Mg/Al dissimilar alloy friction stir weld were studied.The main research results of this paper are:?1?The intermetallic compound produced by friction stir welding for Mg/Al alloy was calculated by the first principle.It is found that the phases of Mg₂₃Al₃₀,MgCu₂ and Al₂Cu are ductile phases,and Mg₁₇Al₁₂ and AlCu are brittle phase on the base of the value G\B calculated.?2?The influence factors are: feed rate,copper foil thickness,rotation speed and offset in successively,the optimum scheme is feed rate 100 mm / min,rotation speed 1000 r/min,the stirring needle is not offset,the thickness 0.01 mm.the tensile strength is up to 121.2MPa,the hardness distribution of the welded joint is approximately '?',the fracture way of the joint is tough-brittle fracture type.?3?The influence of microstructure and properties of friction stir welding for Mg / Al dissimilar alloys by interface alloying is that the weld tensile strength is worst at the feed rate of 200 mm/min,and are better at the feed rate of 100 mm/min and 300 mm/min;with the increase thickness of the added copper foil,the tensile strength of the welded joint decreases in turn.