Evaluating the Effect of Hot-Rolling Reduction on the Mechanical Properties of In Situ Formed Aluminum-Magnesium-Silicon (Al-Mg2Si) Composites

The effects of hot rolling on the microstructure and mechanical properties of as-cast Al-15Mg(2)Si, Al-20Mg(2)Si, and modified Al-15Mg(2)Si in situ composites are studied. During rolling, the primary and eutectic Mg2Si particles undergo mechanical fragmentation and move along the rolling direction, which results in the enhancement of ductility of the composite compared to the as-cast state. At high reductions in thickness, however, severely elongated grains and some cracks are observed in the matrix, which are related to the retardation effect of the widely dispersed particles and also fast cooling of sheets during rolling. These effects are found to be responsible for the observed high tensile strength and low ductility of heavily rolled sheets. It is revealed that the strength-ductility balance of the hot-rolled sheets, as measured by the tensile toughness, is inferior compared to that of the commercially pure Al sheet as the basis for comparison. Therefore, relatively low reductions in thickness are recommended for processing of these composites. The hot extrusion of these composites is also briefly discussed, and it is characterized as a viable route for processing of these composites to achieve high tensile strength with acceptable ductility.