Computational study of cooling rates and recrystallization kinetics in short pulse laser quenching of metal targets

Short pulse laser melting and resolidification of a metal target are investigated in continuum and atomistic computer simulations. The cooling rates achievable in laser quenching are calculated within the framework of two-temperature model for a range of laser fluences and pulse durations. A well-defined maximum in the cooling rate dependence on the pulse duration and fluence is observed and explained by the competition between the electronic heat conduction and the energy transfer from the electrons to the lattice due to the electron-phonon coupling. The results of molecular dynamics simulations demonstrate that the short pulse laser melting and recrystallization take place under highly non-equilibrium conditions that have a strong effect on the time-scales, rates, and other parameters of all the involved processes. An emission of partial dislocations from the melting front and their retreat at later times is observed in the simulations.