Abstract
In this part of the current series, the rheological model developed in Part 1 is applied to study the transient state behaviour of semisolid metal (SSM) slurries under various deformation conditions, such as isothermal shearing, isothermal resting, isostructural shearing, and shear rate transient and cyclic shearing. The theoretical analysis demonstrated that there is a very close coupling between the slurry structure and the apparent viscosity. Irrespective of the flow conditions, the apparent viscosity of a SSM slurry with a specified solid fraction is exclusively determined by its structure, while the effect of shear rate and shearing time is reflected by their effect on slurry structure. For a SSM slurry with spherical solid particles, the deagglomeration time is of the order of a few seconds, while the agglomeration time is of the order of a few thousands of seconds, indicating that the deagglomeration kinetics is about three orders of magnitude faster than the agglomeration kinetics. The present model has also been successfully applied to predict the hysteresis loops under various cyclic deformation conditions. Theoretical predictions have shown that the physical origin of thixotropy lies in the fact that the deagglomeration kinetics of SSM slurries is much faster than the agglomeration kinetics. A suspension will not exhibit thixotropic characteristics if there is no structural change during the shear deformation, or even if there is structural change but the rates of agglomeration and deagglomeration are equal.
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