Modification of the electrochemical properties of 2050-T8 aluminium alloys by a LSP surface treatment

Abstract

2050 is a newly developed aeronautical AlCuLi aluminium alloy with numerous applications such as fuselage of civil aircrafts, and a good mechanical resistance, compared to other aluminium alloys. However, this material is susceptible to pitting corrosion in chloride environment [1], with a possible extension to fatigue crack initiation. Laser-shock processing with various experimental conditions (power density between 4 and 8 GW/cm2, overlapping rate of 33%, 50 % and 66%) was applied to modify the surface reactivity of 2050-T8 alloy. Surface characterizations were carried out at a global scale and a local scale, including nanoindentation tests, X-ray diffraction and grazing x-ray diffraction analysis, AFM surface profiles, and electrochemical tests on large areas (12 mm diameter) and small areas (50 µm diameter) located either on the Al matrix or on the AlFeCu precipitates. Finite element simulations were also proposed to validate residual stress determinations, and analyse surface heterogeneities induced by LSP. At the end, correlations were done between morphological and mechanical surface states, and electrochemical reactivity in chloride environment, revealing a mechano-electrochemical sensitivity particularly pronounced on the cathodic parts of I=f(E) potentio-kinetic curves.2050 is a newly developed aeronautical AlCuLi aluminium alloy with numerous applications such as fuselage of civil aircrafts, and a good mechanical resistance, compared to other aluminium alloys. However, this material is susceptible to pitting corrosion in chloride environment [1], with a possible extension to fatigue crack initiation. Laser-shock processing with various experimental conditions (power density between 4 and 8 GW/cm2, overlapping rate of 33%, 50 % and 66%) was applied to modify the surface reactivity of 2050-T8 alloy. Surface characterizations were carried out at a global scale and a local scale, including nanoindentation tests, X-ray diffraction and grazing x-ray diffraction analysis, AFM surface profiles, and electrochemical tests on large areas (12 mm diameter) and small areas (50 µm diameter) located either on the Al matrix or on the AlFeCu precipitates. Finite element simulations were also proposed to validate residual stress determinations, and analyse surface heterogeneities induced...