抄録
The shape change of AlFeSi compound and the toughness of cast aluminium alloys has been investigated as a function of Fe and Cr content and cooling rate. The needle-like of AlFeSi compounds are generally crystallized, but by the Cr addition, it changed to Chinese scripts. The presence of 0.2 mass % Cr in the alloy up to 0.3 mass % Fe is transformed the AlFeSi compound shape into the Chinese script. The Fe content exceeds 0.5 mass % , Cr content was necessary above 0.4 mass % . Without Cr addition, impact values are dropped rapidly as the Fe content increased up to 0.5 mass %. But, Cr addition was modified the AlFeSi compound from the needle to Chinese script and was resulted restoration of the impact properties. This effect of Cr addition for the impact values was larger in the Fe content up to 0.5 mass % . But, more than 0.5 mass % Fe, improvement effect decreased because of coarsed Al (Fe, Cr) Si compounds. Their coarsed Al (Fe, Cr) Si compounds act as large stress so alloys strength is weakened. By the rapid cooling rate, the change from needle-like to Chinese script of AlFeSi compound is promoted. Impact values are also improved by rapid cooling rate and Cr addition.
