Effects Of Alloying Elements On Microstructure And Properties Of Cu-al Friction Stir Welding Seams

In this study,friction stir welding experiments were carried out on 4mm thick Al-40Cu-xEr alloy,Al-Er alloy and pure Cu.Through the study,the change rules of the structure evolution and mechanical properties of the friction stir welding of copper and aluminum with the addition of Er were revealed,and the technological parameters and the addition of Er were optimized to obtain a good friction stir welding seam.Firstly,the as-cast microstructure of Al-40Cu alloy with different contents of Er and Gd was studied.The addition of rare earth element Er into the Al-40Cu hypereutectic alloy can effectively refine the primary Al2Cu phase.Although the addition of Gd element can also refine the primary Al2Cu phase,the refining effect is worse than Er element,and the volume fraction of the primary Al2Cu phase does not change significantly.The addition of 0.7%Er can reduce the average grain size from 105 ?m of Al-40Cu alloy to about 30 ?m,observably reduce the volume fraction of primary Al2Cu phase,and improve the morphology of Al2Cu phase,which is refined from the thick needle flake to irregular cell.The hard and brittle Al-40Cu-xEr alloy can obtain a well-formed FSW weld with a welding speed of 5 mm/min and a rotating speed of 2000 r/min.The Al2Cu phase and eutectic structure of the base material are transformed into fine equiaxed crystal structure.The tensile strength of the friction stir welding seam of Al-40Cu-0.7Er alloy is 14.7 MPa.The addition of Er prevents the growth of dynamic recrystallization grains,and the size of dynamic recrystallization grains decreases,and the Al2Cu-Al4Cu9 layer at the Al/Cu interface becomes continuous and uniform.Under the same process parameters,the tensile strength and elongation of Al-1.4Er alloy and pure Cu friction stir welding seam are the largest,the tensile strength is about 82 MPa,the elongation is about 5%.