Effect of laser irradiation on carbon implanted copper substrates

We have analyzed the nonequilibrium thermal effects of pulsed nanosecond lasers on carbon implanted copper substrates. The thermal effects of pulsed nanosecond lasers on carbon doped copper substrates were simulated by numerically solving the one-dimensional heat flow equation and taking into account the phase changes which occur at the surface, and temperature and time dependent thermal and optical properties of the irradiated solid. Intense pulsed laser irradiation induces rapid heating at the near-surface resulting in melting, followed by rapid quenching of the melt phase. The effect of laser variables (energy density, pulse duration) on the maximum melt depth, melt-in and solidification velocities and transient temperature profiles have been computed. The melting threshold was found to be approximately 1.40 J/cm ² for 15-ns laser pulses, and increased to approximately 2.5 J/cm² for 50-ns laser pulses. Maximum melt depths and the surface temperatures were found to increase approximately in a linear manner with pulse energy density. Extremely high average solidification velocities (20-45 m/s) were calculated which may give rise to solute trapping and other nonequilibrium segregation effects.