Mechanical properties and fracture process of SiCw/Mg composites produced by squeeze casting and extrusion

Mechanical properties of SiC whisker reinforced magnesium-matrix composites with random and unidirectional alignment of whiskers produced by squeeze casting and hot extrusion were investigated under room and elevated temperature atmospheres. The use of AE42 alloy instead of pure magnesium as a composite matrix contributes to an improvement of mechanical properties, especially proof stress of the composite. The extruded composites have more excellent mechanical properties such as tensile strength, proof stress and elongation than those of the cast composites at room temperature. At elevated temperatures, however, a remarkable decrease of tensile strength and proof stress, and an increase of elongation take place for the extruded composites than for the cast composites. The fracture occurs by cracks which propagate from the whisker/matrix interface debonded at whisker ends to matrix at temperatures lower than 473 K. On the other hand, the fracture takes place by cracks propagating through the matrix/whisker interface at above 473 K.