Study On Formation And Mechanical Properties Of Al/Cu Friction Stir Rivet Welding Joint

The friction stir rivet welding(FSRW)is a kind of joining technology developed on the basis of friction stir welding.It combines mechanical riveting and metallurgical bonding.The FSRW test was carried out on 2 mm thick 1060 aluminum and T2 copper.The effect of welding parameters on the forming and mechanical properties of the joint was studied,and the mechanical properties of the joint were improved by optimizing welding parameters.The conclusions are as follows:The formation of the Al/Cu dissimilar metals FSRW joint appears well.The keyhole at the center of joint.The complete joint was formed by mechanical interlocking and metallurgical combination between aluminum and copper.When welding heat input is insufficient,kissing bond will appear at the cooper/cooper interface.That continuous Intermetallic compound(IMC)layer can be obtained by atomic diffusion between aluminum and copper interfaces.The copper-side continuous IMC layer is CuAl.The aluminum-side continuous IMC layer is CuAl2.The microhardness of the upper plate of FSRW joint increased from the aluminum base metal to the keyhole.The microhardness of the lower plate increase first and then decrease with the increase of the distance from the center of the joint.With the increase of welding heat input,the overall microhardness value of the upper plate increases first and then decreases.The overall microhardness value of the lower plate does not change significantly.The tensile shear load of the joint increases first and then decreases with the increase of welding heat input.All joints are fractured at the lap interface,which belongs to the shear fracture mode.When the parameters are not good,the fracture mode is plastic and brittle mixed fracture.When the parameters are appropriate,the fracture mode is plastic fracture.The results show that the descending sequence about the influence of process parameters on the maximum tensile shear load of joint is shoulder plunge depth,dwell time and rotational speed.The contribution rate of shaft shoulder pressure is more than 50%.The optimized process parameters are rotational speed of 1200 rpm,dwell time of 15 s and shoulder plunge depth of 0.1 mm,and the tensile and shear load of the joint can reach 5.517 kN.