Shape changes of spheroidal and rectangular grains driven by excess free energy

Shape changes occurring in spheroidal and rectangular solid grains were theoretically investigated on the basis of the free energy theory for material transport. It was assumed that material transport in a non-equilibrium system was driven by excess free energy so that the system becomes an equilibrium state. The rate equation for material transport of solid in a non-equilibrium state was derived from this assumption. Using the equation, rates of shape changes for spheroidal and rectangular grains were formulated. From the rate equations, shape changes toward equilibrium shapes were simulated. It was found that elongated grains change their shapes more rapidly than nearly round and cubic grains.