Effect Of Ti, Zr Microalloying Welding Wires On The Microstructure And Properties Of 2A12 Aluminum Alloy Welds

2A12 aluminum alloys are widely used in the aerospace, radar antenna, transportation and other industrial applications with good comprehensive mechanical properties. But the hot crack can be produced and the strength, plasticity of joint will be lower with 2A12 aluminum alloys welding. Grain refinement is one of the most effective means to increase the welded joint strength, plasticity and achieve comprehensive mechanical properties. At present the common method is to add inoculants to refine the microstructure of weld metal.Firstly, this article is to investigate the microstructure and mechanical properties by separately and compound adding trace Ti, Zr elements into Al-Cu alloys. To weld 2A12 aluminum alloy with 4 kinds of aluminum copper alloy welding wire, which are designed according to the above, after optimizing the TIG welding parameters. Study on the effect of different content of Ti, Zr of the welding wires on the microstructure and properties of 2A12 aluminum alloy welds. The major findings have been made as following:Without any inoculants in Al-Cu alloys, the microstructure of alloy is made of coarsely branches crystal; When 0.3%Ti or 0.3%Zr element is added alone, the microstructure of alloy is finer, which showed fine equiaxed grain, the grain size compared to the alloy without Ti, Zr had a significant decrease. When 0.1%Ti, 0.1%Zr is added compositely, the refinement effect is better than the Ti or Zr element is added alone. The grain size is further refined when 0.3%Ti, 0.3%Zr composite is added, but the microstructure has coarse precipitated phase precipitation and precipitation of partial poly, resulting in the tensile strength of the alloy decreased.With the method of TIG welding, the weld fusion width and pe netration increases gradually when the welding current increased; the weld width and weld depth decreases gradually when the welding speed increased. It can obtain a good weld shape when the welding current is 81 A, the welding speed is 2.27mm/s.With increasing of Ti, Zr content in the weld wire, the weld microstructure is gradually refined. The effect of compound inoculants Ti and Zr o n 2A12 alloy weld metal refining is compatible. Al3 Ti and Al3 Zr phase formed in the weld metal will be the heterogeneous nuclei to promote the microstructure refinement when the welding wires with less content of inoculants Ti and Zr. When the composite content of Ti and Zr is higher in the welding wire, except for the finer Al3 Ti and Al3 Zr phase acting as heterogeneous nuclei, the complex compounds Al3(Ti, Zr) phase formed in the weld metal can also be the heterogeneous nuclei and promote the weld microstructure refinement. When w(Ti)=0.248% and w(Zr)=0.244% in welding wire,the weld microstructure is the most tiny, the refinement effect is the best, the joint strength and plasticity is the highest.