Solidification behavior and enhanced properties of semi-solid Al–8Si–0.5Fe alloys fabricated by rheo-diecasting

Abstract

Compared with the high pressure diecasting, rheo-diecasting has an advantage in decreasing defects, refining microstructure and improving properties. In the present work, an Al–8Si–0.5Fe alloy with a good combination of mechanical property and thermal conductivity was obtained by rheo-diecasting. The solidification behavior, mechanical properties, and thermal conductivity of the alloy under rheo-diecasting were discussed. The results demonstrated that the chilling effect and shearing vibration not only affected the primary solidification on the vibrating contraction sloping plate, but also the secondary solidification in the remaining liquid during rheo-diecasting. The rheo-diecasting alloy possessed spherical primary α1-Al grains and secondary α2-Al grains, small-sized Al5FeSi phases, eutectic Si phases, and low porosities, and thus exhibited the high mechanical properties and thermal conductivity. With decreasing pouring temperature from 690 °C to 670 °C, the size of primary α1-Al grains, secondary α2-Al grains, Al5FeSi phases and eutectic Si phases was decreased due to high cooling rate, which further improved the mechanical properties and thermal conductivity of the alloy.