Obstructed shrinkage induces tensio

Obstructed shrinkage induces tension in the mushy zone. The mushy zone most often consists of columnar, though sometimes equiaxed, dendritic grains that are separated from one another by liquid. The semisolid has little strength because the grains are not yet bonded together firmly but still separated by the grain boundary liquid. The problem is that the semisolid also has little ductility during the terminal stage of solidification when the fraction of liquid fL is no longer high enough for the grains to move around and rearrange themselves to accommodate the tensile strain. Thus, cracking can occur along grain boundaries during terminal solidification.