The Microstructure and Mechanical Properties of Multipass Friction Stir‐Welded Al/Cu Lap Joints and Interface Transfer during Butt Joining of Thick Plates

Abstract

Multipass friction stir welding (FSW) is used to obtain an Al/Cu overlap joint. The microstructure and bonding strength of the Al/Cu joints are analyzed. An overlap joint without defect inside the cross section is obtained when the stir pin interval is 3 mm and the plunge depth is 0.2 mm. The welding of the next pass eliminates the “hook” left on the back side of the upper pass, achieving complete welding over a wide area. The stirring pin peels off the Cu surface layer and moves them into Al matrix. Turbulent interactive structures and exfoliated particle interactive structures are formed. Two obvious intermetallic compound layers are formed on the interface and are identified as the Al2Cu and Al4Cu9 phases. The tensile shear strength of the overlap joints with a stir pin interval of 3 mm reaches an average of 95 MPa, which is approximately equal to that of the 1060Al base metal. Moreover, the copper plate coated with the aluminum layer and the aluminum plate are butt joined by conventional FSW to produce an interface transfer. The thick plate (10 mm) butt joint is welded by transferring the original soft–hard (Al/Cu) interface to the soft–soft (Al/Al) interface.

Equal Load-Carrying Design of Lapped Joints of Al–Cu Dissimilar Materials

“…Rheingans et al [ 13 ] studied the relationship between microstructure and temperatures of copper, aluminum, and other materials at the joint, finally optimizing the joint design. Wei et al [ 14 ] obtained Al/Cu lap joint by multi-pass friction stir brazing (FSW),The microstructure and bonding strength of the Al/Cu joint were analyzed, an overlap joint without defect inside the cross section was obtained when the stir pin interval was 3 mm and the plunge depth was 0.2 mm.…”