High strength, high thermal conductivity and wear resistance are required for automotive engine piston. It's known that aluminum borate whisker has high strength and good wear resistance and carbon fiber (CF) has high thermal conductivity. In this study, aluminum borate whisker and two types of CFs, which have difference surface structure, PAN-based CF and Pitch-based CF reinforced JIS-AC8A aluminum alloy and AXE522 magnesium alloy are fabricated by squeeze casting. At first, influence of the surface of CF and the matrix on amount of interface reaction product Al₄C₃ was clarified. Secondly, the influence of Al₄C₃ amount on the bending strength of the composites was examined. As the results, the bending strength of PAN-based CF composites was higher than that of Pitch-based CF composites. Al₄C₃ or Al-O-RE compound was identified by TEM and EDX at the interface of PAN-based CF/AC8A or PAN-based CF/AXE522 respectively. Regardless of AXE522 or AC8A matrix, in PAN-based CF composites, large amount of Al₄C₃ was found compare to Pitch-based CF composites. The bending strength was positively correlated with amount of Al₄C₃. This suggested that the anchor effect by Al₄C₃ would contribute to increasing the strength of the composites.

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  The objective of this study is to investigate carbides in low alloyed ductile cast iron containing less than 3mass%Cr or 2mass%Mo, respectively. All of the carbide in the ductile cast iron containing 3%Cr was Fe₃C, and the carbide in the ductile cast iron containing 2mass%Mo was Fe₃Mo₃C, Mo₂C and Fe₃C. The calculated phase diagram shows that the stable carbides at the room temperature were Cr₇C₃ and Cr₃C₂ in the cast iron containing Cr, or MoC in that containing Mo. Fe₃C or Mo₃Fe₃C which solidified from the molten metal transforms to stable carbide by the in situ nucleation mechanism with decreasing of temperature. The transformation from the unstable to the stable carbide proceeds from the concentration of Cr or Mo in the unstable carbide. Therefore, it is considered that the cooling time of the keel block used in this study was not so long as the stable carbide such as Cr₇C₃ and Cr₃C₂, or Mo₂C precipitate.

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  The authors attempted to use steel can pellets after removing the Al-Mg alloy of can cap parts using differences in the melting point of steel and Al, for melt-casting spheroidal graphite cast iron in a high-frequency furnace. They then examined differences in mechanical properties such as tensile strength and hardness and the microstructure of cast test specimens. Although tensile strength and hardness increased with an increase in the blending ratio of steel can pellets as an iron source, the specimen made by melting only steel can pellets as an iron source showed a remarkable drop in elongation. However, since abnormality in the microstructure was not recognized in all tested specimens, it is thought that material properties did not deteriorate when iron scrap was replaced with steel can pellets within the blending ratio of up to 60%. These test results suggest that steel can pellets used in this experiment can be utilized as a raw material for spheroidal graphite cast iron in blending ratios up to 60%.

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