Modeling of microstructure and microsegregation of U-6%Nb binary alloy during solidification process

By using a modified model of calculating solid fraction, the solid fraction in the solid/liquid interface zone can be expressed by a second order equation with one variable based on calculating phase diagram, instead of assumptions of the position and shape of the solid/liquid interface. Using the model, the solidification microstructure and solute microsegregation of U-6%Nb (mass fraction) binary alloy are simulated. The simulated results show that Nb concentration is the highest at the initially nucleated position. With solidifying, Nb concentration at the nucleus decreases continuously, and at the end of the solidification, poor Nb zones (< 3%) appeared on the grain boundary.