Implementation of a strain-based hot tearing criterion in direct chill cast aluminum ingots

Hot tearing in DC cast AA5182 alloy ingots has been investigated using a total strain-based hot tearing criterion, which has been implemented into a 3-D fully coupled thermal-stress finite element (FE) process model. In this paper, the strain predictions for two ingots cast under different cooling conditions during the start-up phase have been discussed. The strain fields obtained from the model for one of the castings clearly indicate a tendency to accumulate higher magnitudes of tensile strain during solidification on the rolling face, in proximity to the ingot lip. A comparison of predicted plastic strains obtained from the FE model and experimentally determined mushy zone ductility data has also been presented. In a critical region just above the ingot lip, the plastic strain accumulated during solidification may exceed the ductility limit at a temperature of about 575°C, depending on the cooling conditions, and can become susceptible to hot tearing. In contrast, both further up the ingot, and out towards the edge of the rolling face, the accumulated strain has been found to be within the ductility limit of the cast material.