| With the extensive application of aluminum alloy welding components in rail transit,shipping,aerospace,chemical industries,the amount of aluminum alloy welding wires is increasing year by year.According to incomplete statistics,the annual consumption of aluminum alloy welding wire in China exceeds 10,000 tons,ranking first in the world,accounting for one-third of the world’s total demand.However,the variety and specifications of aluminum alloy welding wires in our country are very single.5xxx aluminum alloy welding wire has the best compatibility,therefore,5xxx aluminum alloy welding wire is used to weld almost all types of aluminum alloy base metal,which makes the composition difference between the welding wire and base metal larger,resulting in the unqualified structure and performance of welding joints and welding components.In order to solve this problem,it is urgent to enrich the varieties of aluminum alloy welding wires in China,improve the system of aluminum alloy welding wires,and develop matching welding wires for different aluminum alloy base materials.In this paper,13 kinds of new Al-Mg-Mn series welding wire alloys were designed and 1.2 mm aluminum alloy welding wire suitable for MIG welding was prepared around 5356 aluminum alloy welding wire which is the largest welding amount.The microstructure and mechanical properties of Al-4.7Mg-0.48Mn aluminum alloy welding wire were characterized and analyzed by metallographic microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),tensile test and microhardness test,the effects of zinc content on the microstructure and mechanical properties of Al-4.7Mg-0.48Mn aluminum alloy welding wire were systematically studied,the effects of adding Zr separately,Sc separately and adding Zr and Sc together on the microstructures and mechanical properties of Al-4.5Mg-0.12Mn aluminum alloy welding wire were also studied,based on this,the effects of adding Zr separately,Sc separately and adding Zr and Sc together on the microstructures and mechanical properties of new Al-4.6Mg-0.13Mn-1.01Zn aluminum alloy welding wires were further studied.By comparing the microstructures and mechanical properties of aluminum alloy welding wires,several kinds of aluminum alloy welding wires were optimized,and the annealed 5083 sheets with 6 mm thickness was welded by automatic wire feeding and inert gas shielded arc welding.The weldability of several kinds of optimized welding wires was studied by combining the microstructures and properties of welded joints.The main results were shown as follows:(1)There are excess(FeMn)Al6 phase particles with a size about 1-3 micron in point in Al-4.7Mg-0.48Mn-(0-1.38)Zn finished welding wire,the grain of the finished welding wire is fibrous.The increase of Zn and Zn content has no obvious effect on the configuration of excess phase particles and grain shape and size of(FeMn)Al6.With the increase of Zn content,the tensile strength and yield strength of Al-4.7Mg-0.48Mn-(0-1.38)Zn finished welding wire increase gradually,but its elongation decreases gradually.The optimum content of Zn in Al-4.7Mg-0.48Mn welding wire is 0.99%.The tensile strength,yield strength,and elongation of the Al-4.7Mg-0.48Mn-0.99Zn welding wire are 412.0 MPa,343.5 MPa and 5.8%.(2)There are many excess(FeMn)Al6 phase particles with a size of micron scale punctate in Al-4.5Mg-0.12Mn finished wire with 0.08%Zr,0.045%Sc and 0.11%Zr+0.05%Sc,among which there are excess phase particles of micron scale AlTiZr in finished wire containing Zr;the grains of four kinds of finished welding wires are fibrous,and the grain diameter of Al-4.5Mg-0.12Mn finished welding wire containing Zr is finer.Adding 0.045%Sc alone has no obvious effect on the grain shape and size of Al-4.5Mg-0.12Mn finished welding wire.The optimum composition of the welding wire is Al-4.5Mg-0.12Mn-0.08Zr,the tensile strength,yield strength,and elongation of the Al-4.5Mg-0.12Mn-0.08Zr welding wire are 388.5 MPa,338.2 MPa,and 5.8%.(3)There are many excesses(FeMn)Al6 phase particles of with a size of micron scale punctate in Al-4.6Mg-0.13Mn-1.01Zn finished welding wires with 0.12%Zr,0.046%Sc and 0.13%Zr+0.048%Sc.Among them,there are also excess phase particles of micron scale AlTiZr in the finished welding wires containing Zr;the grains of four kinds of finished welding wires are fibrous,and the grain of Al-4.6Mg-0.13Mn-1.01Zn finished welding wire containing Zr is finer.Adding 0.046%Sc alone has no obvious effect on the grain shape and size of Al-4.6Mg-0.13Mn-1.01Zn finished welding wire.The optimum composition of the welding wire is Al-4.6Mg-0.13Mn-1.01Zn-0.12Zr,the tensile strength,yield strength and elongation of the Al-4.6Mg-0.13Mn-1.01Zn-0.12Zr welding wire are 413.0 MPa,345.3 MPa and 5.3%.(4)It was found that when using the optimized Al-4.62Mg-0.48Mn-0.99Zn,Al-4.53Mg-0.13Mn-0.08Zr and Al-4.7Mg-0.14Mn-1.02Zn-0.12Zr welding wires to welding the 5083-O sheets with 6 mm thick:the grains in the weld zone of welded joints with Zr welding wires are all equiaxed grains which size is 50 microns,while those without Zr welding wires are equiaxed grains which size is 80 microns;there are micron scale(FeMn)Al6 particles and dotted AlTiZr phases in the weld zone of welded joints formed by Zr-containing welding wires.Among them,there are a few micron scales dotted τ(Al2Mg3Zn3)phases in the weld zone formed by Zn-containing aluminum alloy welding wires;microhardness of weld zone formed by Zr-containing welding wire is 3 HV(Al-4.53Mg-0.13Mn-0.08Zr)and 4 HV(Al-4.7Mg-0.14Mn-1.02Zn-0.12Zr)higher than that formed by 5356 aluminum alloy welding wire,the welded joints formed by zinc-containing welding wires have obvious natural aging strengthening ability,when parked at room temperature for 50 days,the microhardness of the weld zone of the two welded joints increased by 6 HV(Al-4.62Mg-0.48Mn-0.99Zn)and 9 HV(Al-4.7Mg-0.14Mn-1.02Zn-0.12Zr)immediately after welding(within 24 hours after welding).When parked at room temperature for 50 days,the tensile strength and yield strength of the Al-4.62Mg-0.48Mn-0.99Zn alloy welding wire formed welded joints increased by 23.6 MPa and 15.2 MPa,compared with 5356 aluminum alloy welding wire formed welded joints. |
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