| In order to exert the complementary advantages of magnesium alloy and titanium alloy and meet the strength requirements while reducing the weight of the structural parts,it is necessary to weld the two metals.TIG welding method has the advantages of good protection effect,simple process,high production efficiency and low cost,and is widely used in non-ferrous metal connection.Due to the large difference in melting point of magnesium and titanium dissimilar metals and poor metallurgical compatibility,the joint performance obtained by the traditional TIG fusion welding technology is difficult to meet the requirements of high-performance welding parts.In this paper,the welding of AZ31B magnesium alloy and TC4 titanium alloy was carried out by TIG welding method,aiming at expanding the interface area and modulating the interface bonding force.Based on the idea of adjusting the welding heat input and improving the spreading ability of the weld metal on the surface of titanium,on the basis of optimizing the welding process,good weld welds welded joints were obtained by adding aluminum and copper intermediate layer between the base materials,and comparison of different materials was analysis The spread properties of the weld metal in the joint,microstructure and the mechanical properties and the corrosion resistance of the joints were compared and analyzed.The results showed that:(1)Under the condition of welding alternating current of 70 A,welding speed of 100 mm/min,welding gun and weld was 60°-70° angle,a good surface magnesium/titanium fusion welding joint was obtained.The brazing joint consisted of interface bonding zone,weld zone and heat affected zone.(2)The interlayer material had a great influence on the spreading properties of the weld metal on the surface of titanium alloy.The wetting angle of weld metal and titanium in the non-interlayer joints,Al interlayer joints and Cu interlayer joints were decreased by 55°,45°and 30° respectively,and the length of interface bonding zone was increased by 5 mm,7 mm,9 mm.(3)For the non-interlayer magnesium/titanium weld brazing joint,the microstructure of the weld zone was mainly composed of a-Mg matrix and Mg17Al12 reinforced phase.The weak bonding between magnesium and titanium connect by the interfacial binding region with a small amount of Al-containing a-Ti solid solution Ti-Al intermetallic compounds,fracture appear in there,and the line tensile strength was only 187.33 N/mm.The hardness of the magnesium matrix in the heat affected zone adjacent to the weld was 15%lower than that of the base metal.(4)Compared with non-interlayer joints,the number of Mg-Al eutectic and Mg17Al12 phases in the weld zone of al-interlayer joint increases and the hardness increases accordingly.The tensile strength of the joint was 279.33 N/mm and increased by 49%.The fracture surface is located in the weld zone,showing a brittle-ductile mixed fracture.(5)Compared with the non-interlayer magnesium/titanium fused joint,the Ti-based solid solution containing A1 and Cu was formed in the interface bonding region of Cu-interlayer joint,and the amount of eutectic in the weld zone increased obviously.The heat affected zone forms a grain boundary permeation zone with a width of 0.35 mm,in which the compound along the grain boundary of the matrix suppresses the grain growth of the a-Mg matrix and has a certain strengthening effect.The hardness of the region is increased by 45%than that of the magnesium alloy.The tensile strength of the joint was up to 432.67 N/mm,which was 1.3 times higher than that of the unclamped joint.(6)The corrosion current density of the weld zone of Cu interlayer,Al interlayer non-interlayer joint decrease in turn,and the corrosion resistance of the weld was enhanced. |
