Phase Transformations by Nanosecond Iodine Laser Pulses

The interaction of intense laser radiation with a metal surface in vacuum is a complicated process which involves surface melting, vaporisation, plasma formation, plasma heating and finally a breakdown or explosion of the superheated plasma. The explosion of the plasma causes a high-pressure shock wave, which acts as an impact on the material. The generated stress wave propagates and is absorbed in the material, causing elastic and plastic deformation, formation of dislocations, slip bands or other microstructural changes. Of the materials tested, an austenitic Hadfield manganese-alloyed steel was found to have the strongest tendency for a martensitic phase transformation, induced only by plastic deformation. An Iodine photo-dissociation laser [1] emitting at the wavelength of 1.315 µm was used for the experiments. The pulse duration was typically 1 ns and the pulse energy could be varied between 1–15 Joules.