Influence of cold-rolling and annealing treatments on microstructure and mechanical properties of friction stir-welded Al–Cu joints

Abstract

The influence of post-weld cold-rolling (PWCR) and annealing treatments on microstructure and mechanical properties of the friction stir-welded Al–Cu joints were investigated in detail. The tensile fractures along at the Al–Cu interface in as-welded (AW) joint was effectively inhibited by PWCR. Accordingly, the strength of the dissimilar Al–Cu butt joints significantly increased from 79 MPa to 384 MPa for the AW state and the post-weld cold-rolled treated state, respectively. By the annealing treatment after the PWCR, the elongation of the dissimilar joints was increased from 1.0% to 17.5%, companied with an acceptable decrement of the strength. The optimised distribution of the intermetallic compounds layer at the Al–Cu interface, the reduced property gradients as well as the microstructure refinements, accounts for the improvement of the mechanical performances of the dissimilar Al–Cu joint.