Effect of the Temperature Gradient, Growth Rate, and the Interflake Spacing on the Microhardness in the Directionally Solidified Al-Si Eutectic Alloy

An alloy of composition Al-12.6 wt.% Si was prepared using metals of 99.99% purity. Weighed amounts of aluminium and silicon were melted in the vacuum-melting furnace. This irregular eutectic alloys were directionally solidified upward with a constant growth rate V (8.3×10−3 mm/s) and different temperature gradients G (2.0–7.8 K/mm) and also with a constant temperature gradient G (7.8 K/mm) and different growth rates V (8.3–498.7×10 −3mm/s) in the directional solidification furnace. The interflake spacings λ and microhardness HV were measured from both transverse section and longitudinal section of the specimen. The variations of HV with respect to G, V, and λ have been determined by using the linear regression analysis method. It has been shown that HV increases with the increasing values of G and V. On the other hand HV values decreases with the increasing λ values. The Hall-Petch type relationships obtained in this work have been compared with the previous works.