INFLUENCE OF SOLIDIFICATION RATE ON ELECTRICAL AND MECHANICAL PROPERTIES OF EUTECTIC AND HYPEREUTECTIC AL-SI ALLOYS

Abstract

ABSTRACTEutectic Al–13 wt. % Si and hypereutectic Al-16 wt. % Si were prepared by usingpermanent mould casting technique. Effect of the cooling technique on the castmicrostructure, mechanical properties, and electrical conductivity of Al-Si alloys wasinvestigated by using the conventional water-cooled and air-cooled methods. Themechanical properties such as the yield stress, tensile strength, hardness, andimpact energy were measured at various cooling methods. Microstructure withscanning electron microscope (SEM) and Energy dispersive spectrometer (EDS)analysis of Al-Si alloys have been studied. In addition, the hardness after solutiontreatment at 529 °C for 2 h and artificial ageing at various temperatures 180 °C and210° C for aging time 2- 10 h was measured. The results show enhancement in themechanical and electrical properties for the eutectic Al-13 wt. % Si and hypereutecticAl-16 wt. % Si alloys for the water-cooled over the air-cooled technique. In addition,the largest value of the impact energy (4.91 J) was obtained for the eutectic Al-13 wt.% Si alloys compared to the hypereutectic Al-16 wt. % Si alloys at 3.09 J for watercooled-medium. The total solidification time (TST) of Al 13% wt. Si was longer thanthat time for the hypereutectic Al 16% wt. Si at various cooling mediums. Agingstudies of Al-Si alloys with aging temperatures 180 oC and 210 oC show that thehardness values increased as the silicon content increases. For hypereutectic Al-16wt. % Si at aging temperature 180 oC and aging time 4 h by using water-cooledtechnique, it was observed that the maximum hardness value reached to 100 HRDcompared that value was 87 HRD for the eutectic Al-13 wt. % Si alloy.