Application of a macroscopic model to predict the band segregation induced by shear deformation of semisolid

Semisolid deformation during solicitation can cause some casting defects such as the band segregation. Since the defect formation originates in nature of semisolid, it is of interest to build a model including the nature and to predict the defect formation. In-situ and time- resolve X-ray imaging has proved that rearrangement of solid grains in semisolid dominantly controls deformation and localization of shear strain leads to the band segregation. On the basis of the observations, a macroscopic model, which explicitly includes the rearrangement, is proposed. The model uses two-phase flow model and introduces hydrostatic stresses to express the rearrangement. The model was applied to simple shear of semisolid to confirm instability against shear. Fluctuation of solid fraction gradually increased and consequently shear deformation was localized. The model is also applied to pseudo 2D deformation in a shear cell, of which dimension was the same as that used in the X-ray imaging. The calculation result qualitatively agreed with the experimental results. It was concluded that the model has a potential to simulate the localization of shear and the band segregation. For further improvement, to measure some physical properties, which are closely related to the rearrangement, is required.