Simulation 3D éléments finis des macroségrégations en peau induites par déformations thermomécaniques lors de la solidification d'alliages métalliques

摘要

Macrosegregations are chemical heterogeneities either in the skin or in the center of metallurgical products. These heterogeneities can generate serious troubles during downstream processing. Contrary to other studies which focus on central macrosegregation, our work aims to simulate the skin macrosegregation induced by thermomechanical deformations. Three steps are necessary to build the simulation. The first step consists on simulating macrosegregation at rigid and fixed solid, i.e. without solid deformation. The second step, independent of the first one, aims to simulate the deformation of the solid without macrosegregation. The last step is a combination of the two previous one. All equations are solved by stabilized finite element methods. Each step refers to experiments in order to compare numerical and experimental results. The first step reproduces numerically the macrosegregation observed during Hebditch & Hunt experience. The numerical results are in good agreement with the experimental ones. The second step aims to simulate the deformation of a metallic liquid droplet during its solidification in contact with a copper chill, in microgravtiy. The numerical deformation obtained presents the same trend as the experimental one but in a lower magnitude. The last step is based on El-Bealy experience consisting of a pulsed water cooling of an ingot. The results show concentration variations but the simulation does'nt catch all experimental ones. Computations without macrosegregation point out that our simulations are less sensitive of deformation than the experiment. All simulations were run with binary alloys. Computations have also been run to simulate ternary alloy solidification but without solid deformation.