Bridging ultrashort-pulse laser-induced surface microstructural refinement and functional modification: from peening...

Ultrashort-pulse laser processing enables concurrent surface functionalization and subsurface grain-refinement of metals, yet the interplay between these competing mechanisms remains unresolved. Here, we bridged the gap between the surface peening effect and functional texturing during ultrashort-pulse laser interactions, through systematic experimentation on Ti-6Al-4V across wavelength, pulse duration, and fluence parameter spaces. The laser-induced hierarchical micro/nano surface texturing on Ti-6Al-4V was elucidated through the exploration of pulse width-dependent thermal and non-thermal dominance mechanisms. The intricate subsurface structural transitions underlying the surface modification were unveiled, from peening-induced nano gradient structuring to swelling-driven porous microstructures, corresponding to pulse durations that span from femtosecond to picosecond regimes. This work explores the critical laser intensities for peening-induced subsurface microstructural refinement and swelling-assisted surface texturing, providing significant insights into the underlying mechanisms governing ultrashort-pulse laser processing and opening new avenues for the design and engineering of multifunctional, high-performance metal surfaces.