Solidification of Tilted-Lamellar Eutectic Grains with a Crystal Mosaicity: A Numerical Simulation Approach

In regular binary eutectic alloys, the shape of two-phase solidification microstructures varies between neighboring eutectic grains. This occurs in particular in alloys that present special orientation relationships (ORs) between the two kinds of crystals. In practice, eutectic grains most often present spatial variations of the crystal orientation of a few degrees. The consequences of this “mosaicity” on the growth dynamics are not clear. We present the first steps of a numerical investigation (boundary-integral method) of the dynamics of the so-called locked-lamellar patterns in the presence of a mosaicity. Realistic alloy parameters were used. We simulated a few pairs of lamellae (periodic boundary conditions) with a smoothly modulated anisotropy of the interphase boundaries in the solid. The pattern evolves then toward a steady-state regime with a uniform lamellar tilt angle, but a spatial modulation of the lamella width.