Manufacturing conditions and mechanical properties of alumina short fiber/AZ91D magnesium alloy composites Masaya NAKAGAWA*, Takaki WADA* Shigeharu KAMADO** and Yo KOJIMA** Alumina short fiber/AZ91D magnesium alloy composites are fabricated using a squeeze casting method. In this study, the effect of the graphite lubricant on the preform deformation was investigated. Additionally, macro-and microstructures and mechanical properties of the composites fabricated at the optimum condition are

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... igated. The preform deformation is caused by the ƒ¿ phase that crystallizes near the surface of a die. Namely, the primary ƒ¿ phase accumulates on the preform and disturbs the molten metal infiltration during squeeze casting. As the result, high compressive pressure acts on the preforms and causes the preform deformation. The coefficient of heat transfer becomes a small value by coating the graphite lubricant on the inside of a die. In this case, no ƒ¿ phase crystallizes near the surface of a die before squeeze casting. Therefore, the preform deformation does not occurs. The composites have high tensile strength at the elevated temperature. But the elongation of the composites is very small at temperatures between room temperature and 250•Ž. The T6 treatment improves tensile strength of the composites at room temperature. However, as tensile test temperature raises, the effect of the T6 treatment decreases and subsequently tensile strength of T6treated composites is approximately equal to that of as-cast composites at 250•Ž.