Formation of the defect band in die castings was attributed to
the rheological behavior in the mushy zone [23], in particular to
the shear stress developed during both filling and subsequent
solidification processes. Two transition points during solidi-
fication, namely coherency and maximum packing solid fraction of
dendrites, divided the mushy zone into three regions with different
mechanical behaviors and feeding mechanisms. The resulting
defect band was rationalized by considering the local shear stress,
shear rate, mechanical strength and time available for fluid flow.
The shear band initiated after the local stress reached a peak
magnitude and then expanded its thickness to about 16 meangrain
size during strain softening. Gourlay et al.