Evaluation of dislocation density gradients in femtosecond laser peened metals

Laser peening is a surface treatment technique that improves the mechanical performance of metals used to extend fatigue life and to enhance fatigue strength. Most studies on laser peening have used nanosecond pulsed lasers, which require a sacrificial coating as well as a transparent overlay, while recent studies reported that femtosecond laser peening does not need any protective layer. The physical process is very complex and requires a multi-physics approach. To validate model predictions high spatial-resolution microstructure data are needed to compare the dislocation density in the depth of the material with the estimated density from the local pressure in the shockwave. Five different metals will be considered. The experimental result will help understanding the modeling of this very complex process and open the path for optimal surface treatment processes using fs lasers.