Simulation of the corrosion-induced damage on aluminum alloy 2024 specimens with equivalent surface notches

Abstract

The effect of corrosion environment aggressiveness on the tensile mechanical properties degradation of AA2024-T3 was investigated. Tensile specimens were pre-corroded for various exposure times to different corrosive solutions, i.e., exfoliation corrosion (EXCO) and 3.5 wt. % NaCl. Then they were tested mechanically. In non-corroded specimens, surface notches of various depths were machined to simulate the degradation of the tensile mechanical properties due to the presence of artificial surface defects. A mechanical model was developed to correlate the corrosion-induced tensile ductility degradation due to pitting and possible hydrogen embrittlement with the equivalent artificially induced surface notches. The cases studied for this physical correlation were: a) EXCO exposure with artificial notches, b) EXCO with 3.5 wt.% NaCl exposure and c) 3.5 wt.% NaCl exposure with artificial notches. Higher correlation was noticed for short exposure times for all cases where the dominant degradation mechanism is slight pitting formation. It was found that 1 h EXCO exposure is equivalent to 92 h exposure to NaCl solution regarding the tensile ductility degradation while 24 h EXCO exposure has the same effect on ductility decrease with a 240 μm surface notch or 4000 h exposure to NaCl solution.

Effect of Solution Aggressiveness on the Crack Growth Resistance and Cracking Mechanism of AA2024-T3

“…The 2 h exposure to EXCO solution was selected for further investigation because no essential stress decrease is noticed from the tensile flow curves, while a significant ductility decrease is evident (as was found in Alexopoulos, et al 2 ). The same is noticed in Alexopoulos, et al, 55 for the 24 h exposure in the NaCl solution that was selected for further investigation. The specimens were removed and cleaned with acetone before performing the mechanical testing.…”

“…Typical tensile curves of the pre-corroded specimens of AA2024-T3 exposed to an EXCO solution and a 3.5 wt% NaCl solution are presented in Figures 3(a) and (b), respectively (as presented in Alexopoulos, et al, 2,55 respectively). The nominal stress calculation was based on the nominal cross section of the tensile specimens, namely, width × thickness = 12.5 mm × 3.2 mm.…”