Processing, Microstructure, and Properties of a Mg/Al Bimetal Macrocomposite

A bimetal magnesium/aluminum (Mg/Al) macrocomposite containing millimeter-scale Al core reinforcement was fabricated via casting and hot-extrusion. Characterization revealed that the Al volume fraction was not uniform along the extruded rod length. Major defects were absent, minimal porosity was present and Mg-Al interfacial integrity was good. The thermal stability of macrocomposite sections was marginally improved when compared to pure Mg. Results revealed that the presence of Al core leads to an improvement in average hardness and stiffness of Mg, and an overall improvement in tensile behavior (beyond 7% Al) assessed using work of fracture (WOF) of Mg. For macrocomposite sections containing more than 7% Al, shift in load bearing from Mg to Al at stress levels corresponding to the plastic deformation zone of Mg was indicated in the stepped tensile stress strain curve. An attempt is made to study the effect of presence of mm-scale Al and its variation on the microstructure and mechanical properties of the bimetal Mg/Al macrocomposite.