Laser Peening for Mitigation of Stress Corrosion Cracking at Welds in Marine Aluminum.

摘要

This work examines the use of laser peening (LP) for mitigation of stress corrosion cracking (SCC) in marine grade aluminum alloys (Al-Mg). These alloys can be sensitized during welding and will develop a tensile residual stress in the heat affected zone that may promote SCC in a salt water environment. Metal inert gas welded aluminum alloy 5083 (4.8wt% Mg) plate was laser peened using a variety of laser intensities to create compressive stresses. Mechanical tests were performed to investigate the SCC of the material including slow strain rate testing and potentiostatically driven, salt- water exposure. Microstructural and micromechanical tests were performed to characterize the effects of LP on the microstructure of the material. The slow strain rate testing showed a systematic decrease in ductility with increasing LP intensity. The fracture surfaces on all welded samples were indicative of ductile fracture but with a pre-crack length that scaled inversely with LP intensity. The hardness of the material increased with LP intensity. This work suggests that welded aluminum alloy 5083 does not readily stress corrosion crack. LP does affect the mechanical behavior of the material, but its full effect on stress corrosion behavior requires further study.