Rheological measurements on dense suspensions containing dendrite-like particles.

During alloy solidification, equiaxed dendrites often move within the solidifying liquid. As this motion is one of the main causes of macrosegregation, a deeper understanding of the behavior of suspensions containing dendrite-like particles is particularly important. Inspired by rheological investigations with dense suspensions containing spheres, pressure-imposed rheological measurements using an annular shear cell were performed and applied to suspensions containing 3D-printed dendrite-like particles. The results indicate that the concept of the friction coefficient for spheres can be adapted by using appropriate coefficients and suitably reduced mechanical coherency limits. Consequently, the particle pressure of interacting, moving dendrite-like particles in liquids can be effectively described. However, direct measurement of the shear rate was not possible due to the shallowness of the rheological cell used. Nevertheless, the viscosity of suspension containing dendrite-like particles could be estimated indirectly by adapting the dimensionless friction number originally proposed for suspensions with spheres. An increase in viscosity at the same reduced solid fraction, due to the specific morphology of the dendrite-like particles, is predicted. While spheres predominantly interact by sliding past one another, dendrite-like particles-particularly those with long sidearms-interact mainly through rotation.