The widths of the Heat Affected Zone (HAZ) produced by nanosecond and femtosecond laser pulses applied to metals, measured experimentally in recent experiments, are quantified by numerical simulations. The calculations use the finite element technique in the case of a two-temperature model. In both experiments and simulations, the HAZ width is defined by physical metallurgy considerations. This allows to describe the lateral thermal effects induced by laser-metal interaction, and thus to explain the large difference in microdrilling sharpness between nanosecond and femtosecond pulse duration regimes.
The numerical simulations give a HAZ width of 1.71 µm for Cu, 290 nm for Ni, and 220 nm for Al after femtosecond pulses. In the nanosecond case, the HAZ width becomes 8.34µm for Cu, 1.64µm for Ni, and 3.15µm for Al. This outlines the difference between the HAZ produced by these two pulse duration regimes (a 6-times to 23-times factor is obtained).
Experimental results obtained on Al samples are finally compared with the numerical results. A reasonable agreement is obtained. This validates the use of a two-temperature model to represent the laser-metal interaction in ultra-short pulse duration regimes.