Influence On Mg,Zr,Er And Ag To The Welding Performance Of 5xxx Aluminum Alloy Welding Wire

The thesis aims at the effect of minor Er, Zr, Ag and Mg on microstructure and mechanical properties of Al-Mg alloy (5183,5356) welded joints. Due to the existence of softening in welded joints of Al-Mg alloy, the minor of Er, Zr and Ag are added, and the amount of Mg are adjusted to welding wires. The microstructure and mechanical properties of two kinds of welded joints, the different amount of Mg and micro-alloying ones, are compared to make sure the fact that tensile strength and yield strength of welded joints can be improved by conducting the experiment.The welded wires used in experiment are produced in two ways:first, the amount of Mg is adjusted; second, minor Zr, Er and Ag are added in traditional Al alloy (5183,5356). The welded wires are producted based on the process of copper casting, extrusion, drawing, surface treatment. And the 7A52 alloys were welded using the method of ac tungsten inert gases welding.Compared the traditional wires with the ones with different amount Mg, it has found that the amount of Mg has little influence on the microstructure. However,addition of Er, Zr and Ag refine the grain size after extrusion. Fine equiaxed grains are dominated in weld zone of alloy joints, and the growth area of columnar crystal in fusion zone is increased. Besides, the microstructure in boundary of welded joints transit smoothly, and the directivity is less obvious.Compared with the mechanical properties of several welded joints, the strength increases with the Mg. And the hardness, tensile strength and yield strength of the welded joints that add Zr, Er and Ag are all better than that of the traditional welded Al-Mg alloy (5183, 5356).In the mechanical tests of 7A52, the tensile strength of the welded joints that add 0.1% Ag are the highest, and is 73.8% of the masters. While the yield strength of the welded joints that add 0.1% Ag are the highest among all the samples.