Laser shock processing of Ti–6Al–4V alloy

Laser shock processing of Ti–6Al–4V alloy is considered. A mathematical model governing the laser non-conduction-limited heating is introduced and a numerical solution for the temperature distribution is presented. The pressure (recoil pressure) generated across the solid–vapour interface is determined and it is considered as an impact load for the elastic–plastic wave generation in the surface region of the substrate material. The depth of the plastic region is predicted from the elastic–plastic wave propagation analysis. An experiment is carried out to ablate the surface using a neodymium-doped yttrium aluminium garnet laser with 8 ns pulse length and 0.5 J energy content. Scanning electron microscopy is carried out to examine the surface morphology of the irradiated region. It is found that microhardness increases by 1 : 5 times the base hardness of the substrate material. The depth of the plastic region predicted extends 0.195 mm from the surface, which agrees well with the experimental findings. In addition, some localized microcracks are observed at the surface of the workpiece.