Study On The Technology And Performance Of PS7055 / 6013 Dissimilar Aluminum Alloy By Friction Stir Welding

Due to the differences of chemical composition and microstructure in spray forming7055aluminum alloy and6013aluminum alloy, fusion welded joint of dissimilar alloy mayappear poor integration within the joint, segregation of alloying elements and other issues.Friction stir welding is a solid connection technology, the melting of metal does not exist, itis one of the most effective ways to solve the problem of welding of dissimilar aluminumalloy.Friction stir welding process and performance test for spray forming7055aluminumalloy and6013aluminum alloy were conducted. OM, SEM, EDS and other methods ofmicroscopic analysis were applied to analysis the microstructure of joint, Hardness of jointwas measured. By interchanging the material in the advancing side and retreat side, themechanism of stir and shoulder to transfer metal in friction stir welding process wasstudied. The results show as follows, when the rotational speed is1200rpm and weldingspeed is150mm/min, the joint with good surface forming was got. Microscopic analysisrevealed the presence and distribution of7055aluminum alloy and6013aluminum alloy injoint. Onion rings structure with the mechanical mixing of the two metals was find in theinternal welds, other areas are filled by mostly single-component metal.Tensile test wasdone, the samples broken at side of the6013heat-affected zone, this area is the weak areas.The fracture type of welded joints is dimple fracture with the rotation speed of600rpm~1200rpm, when the welding speed is1350rpm, it transforms to quasi-cleavagefracture;When dissimilar aluminum alloy was welded at a rotation speed of1200rpm andtravel speed of150mm/min, the tensile reaches283MPa, which is74%compared with6013metal. The hardness of the joint area was measured, the maximum hardness wasfound in the weld nugget area, the hardness increase from7055aluminum metal to nugget.There is a sudden increase in the nugget area, because the recrystallization of grains in thisarea, the grains are extremely fine. From the weld zone to the6013base metal, thehardness continues to increase. This is because the6013thermo-mechanically affectedzone(TMAZ) and heat affected zone (HAZ) suffers from welding thermal cycle, thesecond phase particles precipitate coarsening, solid solution strengthening and workhardening effect disappears in TMAZ and HAZ. A large number of coarse second phaseparticles was found in the TMAZ and HAZ of6013aluminum alloy, the coarsening and precipitates of second phase in thermo-mechanically affected zone and heat affected zonebrittle; The size of the second-phase particles in7055TMAZ and7055HAZ is same withthat in7055base metal. The second-phase particles in nugget is smaller, the density ofsecond phase particles also increases.it was find there is a diffusion of the alloyingelements at the interface, the diffusion of the alloy is more obvious in weld nugget.