SEMI-SOLID HEAT TREATMENT OF HYPEREUTECTIC AL-18% SI ALLOY CONTAINING IRON-RICH INTERMETALLICS

M. Ramadan, N. Fathy, M. A. Waly, A. A. Nofal

Abstract: In this research the effect of semi-solid heat treatment on matrix structure and iron-rich intermetallics of hyper-eutectic Al-18% Si containing 0.95%Fe is studied. Semi-solid heat treatment at heating temperature of 585 ?C shows a significant refinement of ironrich intermetallic phase. In as cast samples ,needle-like iron-rich intermetallics phases was observed, otherwise, plate-like and fine plate-like iron-rich intermetallics phases was observed for all samples heat treated in semi-solid state. Hardness values for semi-solid heat treated Al-18% Si Alloy for all heating time range (10-40 min) are relatively higher compared with the as cast one. Hardness value of 72.5 HRB is achieved by heating Al-18% Si alloy at heating temperature of 585 ?C for 20 min. At the early stages of heating time (up to 20 min), a significant decreases of weight loss is observed in Al-18% Si alloy when semi-solid isothermal heat treatment was applied at 585? C heating temperature. However, semi-solid isothermal heat treatment performed above heating time of 25 min might result in increases of weight. The optimum semi-solid heating treatment condition was achieved at the temperature of 565?C for the range of 15 to 25 mins.

Keywords: Al-18% Si, Intermetallics, Heat treatment, Microstructure, Semi-solid.

DOI: https://doi.org/10.15623/ijret.2014.0305138