Microstructure and mechanical behavior of a Mg AZ31/Al 7050 laminate composite fabricated by extrusion

In the present study, a well bonded Mg/Al laminate containing a soft Mg AZ31 sleeve and an ultra hard Al 7050 core was successfully fabricated by extrusion directly from the as-cast alloys, with the aim to harden Mg alloys. Microstructure and mechanical behavior of the composite were systematically studied. Our results show that the Mg layer contains a bimodal grain structure. The typical texture of the monolithic Mg alloy extruded plate develop in the Mg layer in Mg/Al laminate with most basal poles parallel to the normal direction (ND) and a small fraction of them close to the transverse direction (TD). The Al layer has high fractions of S {123}〈634〉 and cube {001}〈100〉 texture components. The ultra hard Al layer effectively enhances the yield strength. An Al fraction of 40.2% can enhance the yield strength from 155 MPa to 300 MPa, while only increase the weight by 20%. The relationship between the strength of the Mg/Al composite and the strengths and fractions of the Mg and Al layers was studied. The experimental yield strength of the composite is slightly higher than that predicted by the rule of mixtures, while the predicted ultimate strength greatly differs from the experimental one. The main reason lies in that, during tension of the Mg/Al composite, the Mg and the Al layers fracture before they reach their ultimate strength.