Microstructural characterization of directionally solidified Al13wt.%Mg2Si alloy

In the present work, effect of growth rates on microstructure for directionally solidified Al-13wt. %Mg2Si pseudoeutectic alloy at a constant temperature gradient were studied. The composition of pseuodoeutectic Al-Mg2Si alloy in Al-Mg-Si system was chosen to be Al13wt.%Mg2Si (Al–8.75wt.%Mg–4.25wt.%Si) to growth the eutectic phases from ternary liquid.Directional solidification process were carried out with different growth rates (V8.33–175.0 µm/s) at a constant temperature gradient (G6.63 K/mm) by using synchronous motors running at different speed by Bridgman-type furnace.According to phase diagrams and EDX results light grey, black and dark grey phases were identified as quenched liquid phase, Mg2Si coral-like and –Al matrix, respectively.As the growth rate is increased, the eutectic spacings decrease. When the growth rate of samples increases from 8.33 to 175 m/s the average eutectic spacing for Mg Si 2 decrease from 7.12 to 1.70µm. The highest eutectic spacing was obtained at the minimum growth rate and a constant temperature gradient (V8.33 µm/s, G6.68 K/mm). On the other hand, the smallest eutectic spacing was measured at the maximum value of growth rate and a constant temperature gradient (V175.0 m/s, G6.68 K/mm). The dependency of lamellar spacing () on growth rates (V) were obtained as 0.45 16.95 2 Mg Si V for AlMg2Sipseudoeutectic alloy.The bulk growth rate was also determined as V 2 Mg Si 2 408.96 µm3 /s by using the measured values of Mg Si 2 and V