The new MOOSE Phase Field multiphase system allows easy construction of free energy based phase field models. The animation on the left shows a three phase system with a single concentration parameter. Each phase free energy is minimal at a different concentration value. A radial concentration (height value in the plot) gradient is prescribed as an initial condition. The plot is colored by total free energy density.
Particle rafting can be observed in this phase field simulation with coupled chemical and elastic free energies. The precipitate turns oblate under the compressive strain applied in the vertical direction. The chemically insoluble component diffuses into the matrix driven by the elastic interaction - reducing the strain mismatch.
The animation on the left shows a 3D random walk originating in the center of a sphere, shown until it first crosses the surface of the sphere. This is called a first passage event. The system is rotated around the x axis to keep the particle in a plane parallel to the screen and going through the center of the sphere. That way it always hits the surface of the sphere at the outer perimeter line, making the first passage event more obvious in the 2D representation.