DENSITY, ULTIMATE TENSILE-STRENGTH AND MICROSTRUCTURE OF A SQUEEZE CAST AL-11.8 SI-3 MG-5 GRAPHITE COMPOSITE

This paper deals with the improvements obtained in density, ultimate t ensile strength and microstructure of eutectic Al-Si alloy dispersed w ith 5% graphite particulate, squeeze cast into square plates of 100 x 100 x 15 mm in size. The density and ultimate tensile strength of the composite increased from 2.63 to 2.67 g cm(-3) and from 75 to 145 MN m (-2), respectively, when the composite was subjected to a squeeze pres sure of 50 MPa. Both primary alpha and eutectic silicon are refined ow ing to increased heat transfer, and pas and shrinkage porosities are m inimized with pressurized solidification. The composite melt requires higher squeeze pressure than the matrix alloy. in order to obtain maxi mum possible properties under identical experimental conditions.