Development of high strength suction cast hypereutectic Al–20Si alloy containing gamma alumina and strontium

Abstract

ABSTRACTIn this research, the hypereutectic Al–20Si alloy, containing an optimised amount of 4 wt-% γ-Al2O3 and 0.1 wt-% strontium, was successfully synthesised through the suction casting process. The cooling rate (563 K s−1) involved during solidification was estimated by measuring secondary dendritic arm spacing. As a result, a significant change in the morphology of silicon was observed and also led to the formation of a small fraction of refined α-Al throughout the microstructure. The work demonstrates that high tensile properties in hypereutectic Al–20Si alloys can be achieved without the use of conventional inoculants (such as phosphorus). The suction cast Al–20Si alloy exhibits remarkably enhanced tensile properties of average ultimate tensile strength of 355 MPa and average ductility of 7.1%.