Nanosecond laser surface texturing of Ti-6Al-4V & Al1050: Overview of induced modifications and relevant characterization techniques for structural bonding applications

Laser surface texturing (LST) using nanosecond pulses is an effective approach to modify the surface properties of metallic alloys. This study provides a synthetic overview of the modifications induced by LST on two materials: titanium alloy Ti-6Al-4V and aluminum alloy Al1050. The main goal is to improve the structural bonding performance of the metals. Untreated, laser-textured, and sandblasted samples are compared, and the most relevant characterization techniques to assess these changes are identified. Significant changes in topography, microstructure, and surface chemistry are observed due to the heating of matter generated by a nanosecond laser. Surface topography was analyzed using scanning electron microscopy, digital microscopy, and x-ray tomography, highlighting increased surface roughness and surface complexity. Microstructural alterations were evaluated using electron backscatter diffraction and x-ray diffraction. Local increases in dislocation density were identified via kernel average misorientation mapping, and in Ti-6Al-4V, the formation of a martensitic α′ phase was observed in the subsurface. The increase in the oxygen concentration near the surface was assessed by x-ray photoelectron spectroscopy, light-discharge optical emission spectroscopy, and Auger electron spectroscopy. This multitechnique approach allows a comprehensive understanding of laser-induced transformations in the metallic substrates, allowing to understand the key properties in improving the adhesive bonding.