잔류응력에 따른 알루미늄 공식부식 거동

Abstract

Although crystallographic orientation-dependent corrosion of aluminum is dominated by its crystallographic orientation, surface crystallinity under the deformations caused by residual stresses significantly varies with the corrosion stage. Therefore, analysis of the influences of both crystallographic orientation of aluminum and residual stresses on the corrosion resistance of aluminum at all corrosion stages is necessary. Accordingly, herein, the role of residual stress in the crystallographic orientation-dependent corrosion behavior of aluminum at the pit initiation and propagation stages was investigated. A clear correlation between step dissolution of aluminum, crystallographic orientation of aluminum, and residual stress was experimentally, theoretically, and computationally demonstrated based on work function and first-principles calculations. Aluminum atoms exhibit sequential dissolution behaviors, resulting in step configuration of the surface. Residual stress can slightly restrain or promote pit nucleation at the pit initiation stage depending on its sign. However, on the step surface, residual stress is a primary factor determining the dissolution rates of atoms at the pit propagation stage regardless of the crystallographic orientation. Neighboring coordination numbers and distance between atoms were measured to elucidate the effects of crystallographic orientation and residual stress on the corrosion behavior of aluminum. Results of the theoretical and first-principles calculations were adequately consistent with each other and supported the experimentally determined pit density and depth behaviors. This study clarify the role of residual stress in pitting corrosion of aluminum and further expected to broaden the options to improve the corrosion resistance of parts in various industry.