Analysis of Dislocation Density, Recrystallization, and Residual Stress in 5XXX Aluminum using Laser Peening to mitigate Exfoliation Corrosion

Hepburn and Sons LLC teaming with The Ohio State University, Center for Electron Microscopy and Analysis (CEMAS) propose to research and develop an innovative application of laser peening technology to mitigate exfoliation corrosion, a special type of inter-granular corrosion that occurs on the elongated grain boundaries. Strongly related, these Mg based alloys, when exposed to tensile stresses, corrosive environment, and heat over time can begin to sensitize. Currently, when exfoliation corrosion and sensitization occur beyond repair, the Navy must remove and replace the affected plate, resulting in costly and time-consuming maintenance actions. During this Project, the team proposes to laser peen treat 5XXX samples comparing exfoliation corrosion and sensitization resistance to that of untreated samples by conducting a combination of the following potential tests: ASTM G34 Standard Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys, ASTM G66, Standard Test Method for Visual Assessment of Exfoliation Corrosion Susceptibility of 5XXX Series Aluminum Alloys, and ASTM G67 Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test). Transmission Electron Microscopy (TEM) will be used to characterize the test sample dislocation density.