2016 Volume 56 Issue 8 Pages 1413-1419
The feasibility of reducing macrosegregation via control of the solidified structure was investigated. Factors such as the size and complexity of equiaxed grains, which may influence this macrosegregation, were determined. In the first stage of the project, the influence of mechanical vibration on the complexity of the solidified structure was determined. Al-10 wt.%Cu alloys were used as model alloys. The size of the equiaxed grains varied with the amount of modifier. In addition, the complexity of the morphology of primary aluminum was characterized in terms of the fractal dimension, which was measured by using the box-counting method. The results revealed that the fractal dimension increased with increasing frequency of the vibration. Moreover, the diffusion layer in front of the growing interface may be washed away, owing to this vibration. The consequent decrease in thickness of this layer resulted in an increase in the degree of constitutional undercooling. Therefore, the break-down may occur, and hence complexity of the solid/liquid interface may increase. The results also revealed that the size and complexity of the equiaxed grains may be independently controlled to some extent.