The effects of Fe and Ca additions on impact fatigue characteristics were investigated comparing with their effects on usual fatigue characteristics in AC2B-T6 aluminum casting alloys. Impact fatigue strength in the low cycle life region of a low Fe content sample is greater than that of the high Fe content one. This trend is, however, just opposite to the trend in the high cycle life region. Both impact and usual fatigue strengths, especially in the high cycle life region, increased by refining and spheroidizing of eutectic Si particles and refining of Al-Fe based intermetallic compounds by adding small amount of Ca. They were confirmed by fractographic observation of fatigue crack around eutectic Si particles and Al-Fe system intermetallic compounds on the fatigue fracture surface. The usual fatigue strength is greater than the impact fatigue strength when fatigue strength is characterized by the cumulative duration time of loading.
