Speaker
Description
Channel segregation is one of the most frequently observed segregation patterns in large steel ingots, electro-slag remelting ingots, and as cast superalloys. These segregation defects are often referred to as ‘A’ segregate or lamellar-structured segregate in large steel ingots and ‘freckles’ in vertically solidified castings such as in the process of directionally solidification of superalloy castings. It is widely recognized that the channel segregation is formed by the thermol-solute-fluid flow instability during solidification process, therefore, it is important to gain better understanding of the fluid flow, heat transfer and species transport during solidification processing. Here, we employed the multi-phase solidification model to investigate the chimney behaviour and the evolution of channel segregation from the lateral heat dissipation Pb-Sn benchmark case to both nickel-based single crystal superalloy CMSX-4 and large steel ingot. Although channel segregations are caused by unstable convection of liquid melt into the mushy zone, channel segregations have different behaviors for castings of different materials and sizes, and their formation mechanisms are also different from each other, which will be discussed in current study.