An investigation on twist extrusion followed by forward extrusion in production of aluminum-copper bimetallic bar

Abstract

In this research, the feasibility of making aluminum-copper bimetallic bar by twist extrusion followed by forward extrusion is addressed. In this consecutive process, twist extrusion was used in several passes and its effect was investigated on the bond strength between aluminum and copper as well as the mechanical properties of the produced bimetallic bars. When forward extrusion was the only applied process, the compressive yield and shear bond strength of produced bimetallic bars were 184 MPa and 5.4 MPa, respectively. Applying four twist extrusion passes followed by one forward extrusion pass increased these values such that the compressive yield and shear bond strength were increased by about 64% and 200 %, respectively. The hardness was also significantly increased by the utilization of this procedure. Microstructures of copper and aluminum in the produced bars showed that by applying and repetition of the twist extrusion, the grain size was reduced. The Mechanical locking was the main factor in bond formation. Reducing the gap between the metal plates at the interface and increasing the joint fraction improved the shear bond strength.