Semi-solid metal processing method and a process for casting alloy

Abstract

A magnesium or aluminum alloy melt having a composition within maximum solubility limits is poured into a mold at a temperature exceeding the alloy liquidus line, but not higher by more than 30.degree. C., the melt is cooled at a rate of at least 1.0.degree. C./sec to form a billet, the billet is heated at a rate of at least 0.5.degree. C./min in a range bound by the alloy solubility line and the alloy solidus line and further heated to a temperature above the alloy solidus line and is maintained at that temperature for 5 to 60 minutes, thereby spheroidizing primary crystals thereof, the billet is then further heated to a temperature below the alloy liquidus line and the semi-solid billet is shaped under pressure. Alternatively, a hypo-eutectic aluminum alloy melt having a composition at or above maximum solubility limits is poured into a billet-forming mold at a temperature exceeding the alloy liquidus line, but not higher by more than 30.degree. C. and the melt is cooled at a rate of at least 1.0.degree. C./sec to form a billet, the billet is then heated to a temperature above the alloy eutectic point, the holding time and temperature are selected such that the liquid-phase content of the billet is adjusted to 20% to 80% and primary crystals thereof are spheroidized and, the semi-solid billet having the adjusted liquid-phase content is shaped under pressure.