Microstructure and Mechanical Property of Al 7075/Mg EW75 Composite Prepared by Asymmetric Co-extrusion with Symmetric Die

To improve the microstructure of the Al/Mg composite fabricated by extrusion bonding, a novel method to achieve asymmetric extrusion of Al 7075/Mg EW75 composite is proposed, which uses an off-center setup of the initial billet and symmetric die. Good metallurgical bonding is achieved on the interface by the formation of the Mg₂₃Al₃₀ and Mg₁₇Al₁₂ phases as opposed to the Al₃Mg₂ and Mg₁₇Al₁₂ phases reported before. The asymmetric extrusion promotes recrystallization, refines the microstructure of the matrix, and weakens the strong basal texture of magnesium, which homogenizes the plastic deformation during loading and alleviates the stress concentration on the intermetallic layer. Asymmetric extrusion delays interface crack formation and improves tensile strength of the extruded composite.