Effect of volume fraction and particle size on the microstructure and plastic deformation of Mg–Y2O3 composites

The plastic behaviour at room temperature of magnesium and magnesium metal matrix composites reinforced with yttria particles of two sizes is studied. All the materials are produced by powder metallurgy. During extrusion both the unreinforced magnesium and the composites develop a fibre texture with the {1 0 1¯ 0} planes perpendicular to the extrusion direction. The fibre intensity decreases as the volume fraction of yttria particles increases. A tension/compression asymmetry is observed. The extrusion texture prevents deformation by the basal slip system in both tension and compression. Deformation in the {1 0 1¯ 2}〈1 0 1¯ 1〉 twinning system is only possible in compression. As the volume fraction of yttria particles increases, the texture becomes more random and the tension/compression asymmetry tends to decrease and is eventually reversed. The composites reinforced with the smallest ceramic particles present the highest yield stress.