A new two-phase thermo-mechanical model and its application to the study of hot tearing formation during the start-up phase of DC cast ingots

The purpose of this work is to present a new 2D two-phase simulator for the prediction of hot tearing formation in DC casting of aluminum ingots. In this model, the main mechanisms for the formation of hot tears during solidification, namely thermally-induced deformations, and the lack of liquid feeding to compensate for solidification shrinkage and viscoplastic volumetric dilatation, are addressed simultaneously. In the modeling, the liquid flow, the stresses and the strains in the two-phase mushy zone are calculated using an advanced model for the viscoplastic deformation of the semi-solid material. In the present article, the modeling equations are solved numerically for the direct-chill casting of axi-symmetric aluminum extrusion ingot. In order to study the effect of the casting speed on the formation of center hot-cracks, new hot tearing criteria based on the mechanical quantities resulting from the simulations are compared to experimental results from casting trials with varying the casting speed ramping during the casting process.