Laser-interference pulse number dependence of surface chemistry and sub-surface microstructure of AA2024-T3 alloy

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

“…This technique, recently referred to as Direct Laser Interference Patterning (Lasagni et al 2011;Lasagni et al 2015;Lasagni et al 2017), involves the overlapping of two or more incident laser beams, which originate from a main laser beam on the specimen surface to yield a periodic power distribution on the material surface. This LIS technique using a nano-second laser (Lasagni et al 2007;D'alessandria, Lasagni, and Mücklich 2008) was found to achieve both surface cleaning, i.e., surface contaminant removal, and surface structuring (Sabau, Meyer, and Leonard 2020). The adhesion of Desoprime™ HS CA7233 Military Epoxy Primer on treated CCC, SAA.…”

“…rougher surfaces would require smaller laser energy for interference structuring, (b) smaller periodicities would require larger laser energy for structuring, and (c) smaller ℎ $'( are expected for smaller periodicities. The thermophysical properties for the Al2024 alloy were obtained based on thermodynamic simulation using the Al material database Computherm and microstructure model in ProCAST, as shown in (Sabau, Meyer, and Leonard 2020). The thermophysical property data indicate that Al2024 undergoes phase changes over a very wide range of temperatures (TSolidus=508 o C and TLiquidus=640 o C for the Scheil model).…”

“…The STEM Z-contrast images for as-received and laserinterference processed specimens are shown in Figure 13. The structuring is evident for the 8-shot specimens, as shown in details of the transmission electron microscopy (TEM) foil liftout were shown for the 8-shot specimen in (Sabau, Meyer, and Leonard 2020). Due to the variation in structuring, such as discontinuity in structuring lines (Figure 11), and the nm thickness of TEM specimens, this type STEM characterization is not appropriate to investigate the surface structuring seen in these specimens.…”

“…A WYKO NT9100 surface profilometer was used to obtain surface roughness data for the alloy surfaces in the as-received condition, i.e., without any laser processing, and after laser-interference processing (Appendix A). Due to the space limitation, the topology, microstructure, and surface chemistry are not presented in this study as they were addressed in detail in other publications (Sabau, Jun, and McClurg 2020;Sabau, Meyer, and Leonard 2020) for laser fluences F1 of 1.238 J/cm 2 and are highlighted here for the sake of completion. First, the X-ray photoelectron spectroscopy (XPS) data showed that this laser technique is effective at removal of some surface contaminants, particularly for carbon which was modestly reduced for two laser pulses processing dramatically reduced for eight laser pulses (Sabau, Meyer, and Leonard 2020).…”

“…Due to the space limitation, the topology, microstructure, and surface chemistry are not presented in this study as they were addressed in detail in other publications (Sabau, Jun, and McClurg 2020;Sabau, Meyer, and Leonard 2020) for laser fluences F1 of 1.238 J/cm 2 and are highlighted here for the sake of completion. First, the X-ray photoelectron spectroscopy (XPS) data showed that this laser technique is effective at removal of some surface contaminants, particularly for carbon which was modestly reduced for two laser pulses processing dramatically reduced for eight laser pulses (Sabau, Meyer, and Leonard 2020). Second, the laser-interference processing was found to reduce the formation of CuMn-rich precipitates over a 500-800 nm depth from the top surface, which may lead to an increase in corrosion protection as the localized corrosion would be reduced.…”