Study On Stress Corrosion Behavior And Mechanism Of 5A06 Aluminum Alloy In The Simulated Marine Environment

The ocean contains huge resources,the country has extended its exploration of The ocean harbors extensive resources,and national exploration of its depths had expanded from shallow to deep-sea domains.Nevertheless,the deep-sea environment is intricate and heterogeneous,and the overwhelming majority of materials are unable to endure the substantial pressure and corrosive behavior inherent to such a context.As such,the quest for high-strength and corrosion-resistant alloys is of paramount importance for oceanic development.The 5-series aluminum alloy boasts exceptional corrosion resistance and has received significant attention in shallow waters.Nonetheless,deep-sea equipment is subject not only to seawater pressure but also to stress,and the consequences of failure could be catastrophic.Hence,investigating the stress corrosion behavior of aluminum alloys and elucidating the impact of corrosion is of considerable significance for ensuring the stable operation of deep-sea equipment.In this study,stress values of 10%,50%,and 90%of the material’s yield strength were applied to 5A06 aluminum alloy using the constant load method to investigate the effect of stress on the material.Additionally,the impact of environmental factors such as dissolved oxygen concentration,hydrostatic pressure,and temperature on the stress corrosion behavior of the alloy was examined by adjusting these parameters.The electrochemical properties,apparent corrosion morphology,chemical valence state changes,and sensitivity of the alloy to stress corrosion were analyzed using various electrochemical methods including dynamic polarization,electrochemical impedance spectroscopy,and Mott-Schottky analysis,as well as characterization techniques such as scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray photoelectron spectroscopy（XPS）,and mechanical properties testing,such as slow strain rate tensile tests.The results revealed that under low dissolved oxygen conditions,when 5A06 aluminum alloy was subjected to stress ranging from 10%to 90%,the corrosion potential decreased from-0.64 V to-0.77 V,and the carrier concentration increased from 3.78×10¹⁹ m^-3 to1.81×10²⁰ m^-3.Under high dissolved oxygen conditions,when stress increased from 10%to90%,the corrosion potential decreased from-0.56 V to-0.69 V,and the carrier concentration increased from 1.76×10¹⁹ m^-3 to 6.75×10¹⁹ m^-3.When stress increased from 10%to 90%at 0.1 MPa,the corrosion potential decreased from-0.63 V to-0.71 V,and the carrier concentration increased from 5.75×10¹⁹ m^-3 to6.17×10¹⁹ m^-3.Under 20 MPa conditions,when stress increased from 10%to 90%,the corrosion potential decreased from-0.68 V to-0.74 V,and the carrier concentration increased from 7.80×10²⁰ m^-3 to 2.17×10²¹ m^-3.At a low temperature of 4℃,when stress increased from 10%to 90%,the corrosion potential decreased from-0.57 V to-0.69 V,and the carrier concentration increased from1.76×10¹⁹ m^-3 to 6.76×10¹⁹ m^-3.At room temperature of 25℃,when stress increased from 10%to 90%,the corrosion potential decreased from-0.68 V to-0.78 V,and the carrier concentration increased from 8.62×10¹⁹ m^-3 to 1.52×10²⁰ m^-3.Based on the results of the tensile tests,it had been observed that immersion of the aluminum alloy under different environmental conditions results in a reduction of its tensile strength.Nevertheless,this effect was not pronounced.The stress loss coefficient calculated from the elongation rate and section damage rate reveals that the stress corrosion loss coefficient increased significantly with higher applied stress,which had a substantial impact on the corrosion resistance performance of the aluminum alloy.Using the aforementioned research findings,a function model had been established for the stress corrosion weight loss of 5A06 aluminum alloy.This model was capable of predicting the relationship between stress and weight loss of aluminum alloy in deep sea environments.For instance,it could be utilized to forecast the corrosion behavior of test samples subjected to different stress environments but with identical temperature and dissolved oxygen concentration.