The Master's thesis of researcher Zainab Zahir Mohammed Jawad was discussed at the College of Engineering, University of Basrah, Department of Materials Engineering, under the supervision of Professor Dr. Adnan Shamkhi Jabr, entitled: Effect of different modification methods in Al-Si alloys
This work aims to study the effect of solidification parameters and ultrasonic waves on the Si plates size in eutectic Al-Si alloys. The study was divided into two parts. The first part investigated the effect of solidification parameters namely, the cooling rate, solidification rate, and temperature gradient on the size of the silicon phase in a eutectic Al-Si alloy. Directional solidification was achieved using a copper chiller embedded in a sand mold, producing a gradient of these parameters along the length of the casting. In addition, a numerical simulation based on a finite-difference model was employed to predict the temperature field within the casting. The silicon phase size was quantified by image processing of microstructural images taken at multiple positions along the casting using Image-J software. The results revealed a clear inverse relationship between the solidification parameters and silicon plate size; as the cooling rate, solidification rate, and temperature gradient increased due to the chilling effect, the silicon phase became finer and more uniformly distributed. These findings suggest that rapid cooling through chilling can be effectively used as a method for silicon modification in eutectic Al-Si alloys.
The second part of the work involved casting two cylindrical samples, one under ultrasonication and the other cast without ultrasonication. The lower circular surfaces of the samples were then prepared for microscopic examination. Radial measurements of the silicon phase were conducted using an optical microscope equipped with a digital camera and image processing software. The results demonstrated the effectiveness of ultrasonication in refining and rounding the silicon plates
