MECHANICAL-PROPERTIES AND FRACTURE PROCESS OF SICW MG COMPOSITES PRODUCED BY SQUEEZE CASTING AND EXTRUSION/

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