Characterisation of through-thickness microstructure in centrifugally cast hypereutectic Al-Si and Al-Al3Ni alloys

Abstract

In this study, a series of hypereutectic Al-Si and Al-Al3Ni alloys were manufactured using the centrifugal casting technique. Experimental results showed that there are significant differences in the micro-structural morphology and hardness distribution of centrifugally-cast hypereutectic Al-Si and Al-Al3Ni alloys resulting mainly from the difference in densities of the non-metallic particles (ρ Al3Ni = 4000 kg/m3; ρSi = 2330kg/m3).The solidification structure of the hypereutectic Al-Si pipes can be divided into four specific zones along the through-thickness direction. The primary silicon area fraction and hardness at the outer area are higher than those at the inner area, which are in turn higher than those at the interior region. On the other hand, the solidification structure of the hypereutectic Al-Al3Ni pipes can be roughly divided into two or three solidification zones in order of decreasing primary Al3Ni area fraction from the outer peripheral zone to the inner peripheral zone.In addition, the area fraction of primary particles and the hardness along the through-thickness direction of the pipes could be influenced by the solute content.