The proposed research program is aimed at obtaining a better fundamental understanding of the fast non-equilibrium processes induced by short pulse laser irradiation of a metal target. A multiscale computational model combining atomistic and continuum methods will be developed and applied for investigation of the mechanisms of melting and resolidification occurring under extreme superheating/undercooling conditions realized in short pulse laser processing. The interplay of two competing processes, propagation of the melting front from the surface and homogeneous melting of an overheated sub-surface region, which occur simultaneously with relaxation of the laser-induced pressure, will be analyzed for different irradiation conditions, materials, and crystal faces. The nature of the structural correlations that develop as the liquid is undercooled down to the glass transition temperature and the effect of the crystal-amorphous interface on the structure and stability of the amorphous layer will be investigated. The parameters that define the glass forming ability in laser quenching will be identified based on the simulation results for several representative metallic alloys. The mechanisms of laser ablation and cluster formation under different irradiation conditions will be investigated and suggestions on the optimum experimental conditions for size-selective cluster generation will be made based on the simulation results. The educational component of the proposed program includes incorporation of computational methods and the results of computer modeling into the materials science curriculum, design of a hypertext and educational modules on computational materials science. The hypertext will include a discussion of the major computational methods used in materials science and, at the same time, will provide a stimulating learning environment through the use of interactive on-line simulations and exercises. This research is being supported by the Thermal Transport and Thermal Processing Program of the Chemical and Transport Systems Division.
