Effect of machining‐induced surface integrity on the corrosion behavior of Al–Li alloy 2A97 in sodium chloride solution

Abstract

Al–Li alloy 2A97 is one promising alloy that could be widely used in the aerospace field to achieve weight lighting. Due to the addition of lithium element, its anticorrosion attracts widespread interest. In this study, the milled surfaces and ground‐polished surfaces of alloy 2A97 are characterized and compared from three aspects of surface integrity, namely surface roughness, residual stresses, and work‐hardening. After potentiodynamic polarization measurements that were conducted on the machined samples with different surfaces in 3.5 wt% sodium chloride solution, the corrosion parameters regarding corrosion thermodynamics and kinetics are analyzed. Experimental results reveal that the surface micro‐hardness of the milled surfaces is greater than that of the ground‐polished surfaces because of the plastic deformation induced by milling process. Work‐hardening is beneficial while increasing surface roughness is detrimental to anticorrosion of alloy 2A97, and the effect of surface residual stresses is insignificant. Moreover, the corrosion parameters and surface corrosion morphology indicate that the corrosion resistance of Al–Li alloy 2A97 underwent milling process is superior than that obtained by grinding and subsequently polishing, which could further promote the application of mechanical milling Al–Li alloy process in aerospace industry.