Surface chemistry and composition-induced variation of laser interference-based surface treatment of Al alloys

Laser-Interference Surface Preparation for Enhanced Coating Adhesion and Adhesive Joining of Multi-Materials (Final Project Report)

“…In a previous study on AA5182 alloy (Meyer et al, 2019), it was found that even at 1-shot/spot that the oxide overlayer was thickened compared to the baseline value (75 nm vs. 60 nm). We were surprised that in this case it did not do the same.…”

“…( 4) What is the extent of removal of the initial native oxide? ( 5) What type of oxide grows subsequent to laser-interference treatment, (5) What are the sub-surface microstructural changes?, and (6) what is the corrosion resistance of coated specimens that were prepared using laser-interference techniques? This understanding is necessary to effectively transition non-chemical methods.…”

“…At 355 nm wavelength, the laser pulse duration was ~8 ns. The laser interference power profile was created by splitting the main laser beam and guiding the two beams to the sample surface by overlapping each other with defined angles (Meyer, Sabau, and Daniel 2019). The coherent laser beams create an interference pattern in the overlap spot.…”

“…The coherent laser beams create an interference pattern in the overlap spot. As shown in Figure 3, The laser pulse fluence (pulse energy per unit area) was increased by using identical lenses in each beam path in order to decrease the spot size to 5 mm or 6 mm from the original beam size of 8 mm (Sabau, Greer, et al 2016;Meyer, Sabau, and Daniel 2019). The periodicity between power peaks and the resulting laser-interference induced undulations (d), is defined by the wavelength, λ, and the angle, α, between the two beams, as 𝑑 =…”

“…First, on a previous analysis of a different but similar Al/Mg alloy (Meyer et al, 2019), several repeats on the baseline material were run and gave almost identical results for the depth profiles. Second, in an extended study of this alloy, but not reported in this study, two depth profiles, which were obtained at two different locations on the same sample, showed insignificant differences, aside from the data that was obtained at the top 1-5 nm of the samples since slightly different amounts of carbon were on the outer surface (due to the different packaging of the second specimen).…”