Influence of combined shot peening and PEO treatment on corrosion fatigue behavior of 7A85 aluminum alloy

摘要

The plasma electrolytic oxidation (PEO) with coating thickness of similar to 10 mu m and similar to 35 mu m on 7A85 aluminum alloy was performed using the alkaline silicate based electrolyte, and the corresponding influence on fatigue behavior in air and 3.5% NaCl solution was studied. Results show that PEO treatments reduced the corrosion fatigue life of 7A85 aluminum alloy. The corrosion fatigue life of samples with thin PEO coatings (10 mu m-thick) is decreased for the occluded battery promoted localized corrosion, while that of samples with thicker PEO coatings (35 mu m-thick) is reduced for the low ductility of the oxide coating. The shot peening (SP) treatment with ceramic shots was introduced as pretreatment of PEO, The surface residual stresses as well as the residual stress of the substrate beneath the coating were analyzed by X-ray stress analyzer. The corrosion fatigue performance of shot peening combined PEO treated samples is improved for the residual compressive stress field induced by shot peening. Whereas, enhanced notch effect was induced by shot peeing surface roughening and oxide coating local over-growth, so the corrosion fatigue life of samples with SP, surface polishing, PEO, respectively is further improved for the reduction of notch effect.