Nano gradient structuring at Ti-6Al-4V surface induced by ultrashort-pulse laser peening

We have successfully fabricated gradient micro/nano structuring on the surface top layers of Ti-6Al-4V alloy using a shock-peening technique facilitated by femtosecond and picosecond laser pulses, without the need for coatings or confinement. These micro/nano structures encompass ultrafine grains, extensive subgrain boundaries, hierarchical nanotwins, and complex dislocation morphologies. The ultrafine grains, ranging in size from hundreds of nanometers to a few micrometers, were predominantly located in the grain-refined regions, whereas the micro/nano dislocation structures were predominantly found in regions of severe plastic deformation. These observations suggest a promising avenue for achieving high-precision gradient structuring in the field of metallic surface engineering.