Directional Solidification of Al-Si Irregular Ternary Eutectic Alloy and Thermophysical Properties

Abstract

Directional solidification of Al-11.75 wt pct Si-2.15 wt pct Ti irregular eutectic alloy which has an 843.83 K melting point, was done with different growth rates (V = 8.51 to 2065.18 mu m s(-1)) at a temperature gradient (G) of 8.36 K mm(-1) using Bridgman-type directional solidification apparatus (BTDSA). Scanning electron microscopy (SEM)-Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were used to characterize all phases forming the alloy. The average values of interflake spacing (lambda(T)) were measured from transverse sections of the directionally solidified samples with standard techniques. The dependency of lambda(T) was experimentally obtained using linear regression analysis for low, high, and all growth rates. It was observed that the lambda(T) values tended to decrease with increasing V values; therefore, the interflake structures came closer. The fusion enthalpy (Delta H-f) and specific heat difference between solid and liquid (Delta C-p) for the Al-Si-Ti eutectic alloy were found as 376.12 J g(-1)and 0.659 J g(-1) K-1, respectively, by the differential scanning calorimetry (DSC). All results obtained in the present work were compared with the eutectic theory and the Al-based similar experimental results in the literature. [GRAPHICS] .