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We propose a methodology for the rheological characterization of a semisolidmetal slurry using experimental squeeze flow data. The slurry is modeled as astructural thixotropic viscoplastic material, obeying the regularizedHerschel-Bulkley constitutive equation. All rheological parameters are assumedto vary with the structure parameter that is governed by a first-order kineticsaccounting for the material structure breakdown and build-up. The squeeze flowis simulated using finite elements in a Lagrangian framework. The evolution ofthe sample height has been studied for wide ranges of the Bingham and Reynoldsnumbers, the power-law exponent as well as the kinetics parameters of thestructure parameter. Systematic comparisons have been carried out withavailable experimental data on a semisolid aluminium alloy (A356), where thesample is compressed from its topside under a specified strain of 80% at atemperature of 582 oC while the bottom side remains fixed. Excellent agreementwith the experimental data could be achieved provided that at the initialinstances (up to 0.01s) of the experiment the applied load is much higher thanthe nominal experimental load and that the yield stress and the power-lawexponent vary linearly with the structure parameter. The first assumptionimplies that a different model, such as an elastoviscoplastic one, needs to beemployed during the initial stages of the experiment. As for the second one,the evolution of the sample height can be reproduced allowing the yield stressto vary from 0 (no structure) to a maximum nominal value (full structure) andthe power-law exponent from 0.2 to 1.4, i.e., from the shear-thinning to theshear-thickening regime. These variations are consistent with the internalmicrostructure variation pattern known to be exhibited by semisolid slurries.

Rheological characterization of a thixotropic semisolid slurry by means of numerical simulations of squeeze flow experiments