Nucleation and Growth of Solid Phases with Rectangular Morphology from the Molten Phase Using Laser Irradiation
The paper presents a model to describe the morphology of crystals formed during solidification of a surface layer melted by laser irradiation. The classical models of solidification in undercooled melts assume the formation of a stable spherical nucleus whose size is greater than the critical value, usually called the critical radius. The present paper extends this approach to the more realistic and general case in which the crystal embryo is a rectangular solid. The physical model assumes additive surface and volume free energies to determine the total free energy corresponding to the current size of the embryo. However, the simple derivative of the total free energy with respect to the radius of the spherical nucleus is replaced in the present case by the Lagrange multiplier procedure and the condition of minimizing the surface/volume ratio of the embryo during its growth. Some examples of computer simulation show the results of the model.