| A kind of Al-6.3Cu-l.l(Mn,Zr,Ti,V,Sc,B) welding wire was prepared by adding minor Sc, Zr, Mn, V, B, and was used to weld 2195 aluminum-lithium alloy plate with a composition of Al-4Cu-lLi-0.4Mg-0.54(Ag,Zr,Ti), 2mm in thickness. Mechanical properties and hardness of the welding joint was tested, and microstructure of welding wire and welding joint were observed via OM, XRD, TEM and SEM. Analysis and explanation in theory were also given. The results show that:The first, the mechanical properties of 2195 alloy at T8 treatment are as follows: in transverse.direction, b=551MPa, 0.2=522MPa 5=5.4%, with a parallel facture; in longitudinal direction, b=558MPa, 0.2=528MPa, 5=5.7%, with an oblique facture of 45? At T8 treatment, the main strengthening phase of 2195 alloy is T1(Al2CuLi) phase.The second, the Al-Cu based alloy welding wire prepared by adding minor Sc, Zr, Mn, V, B has a good compaticity with 2195 base metal. Using TIG welding technology, the mechanical properties of the welding joint can reach b=384MPa, 0.2=315MPa, 5=4.2%, and the welding coefficient is 0.70.The third, fine grains are found along the edge of the weld, which is different from the equiaxial dendritic. Its formation has a relationship with the effect of Li, Sc, Zr, Ti on the crystallization of molten pool. Li reduces the surface tension of aluminum luquid obviously, increases the ratio and rate of heterogeneous nucleation, which is the necessary condition of the formation of fine grains. However, a large amount of unmelted Al3Sc, Al3Zr TiAl3 particles dispersively distribute in the luquid metal along the edge of the molten pool, which is the sufficient condition of the formation of fine grains. At the same time, united recrystallization of epitaxial growth in the edge of the molten pool is restrained.Finally, the strength of the weld mainly comes from grain-refining strengthening caused by Sc, Zr, V, Ti, B and precipitation strengthening of '(Al2Cu), Al3Sc, Al3Zr. |
