Comparative study on microstructure and electrochemical corrosion resistance of Al7075 alloy prepared by laser additive manufacturing and forging technology

Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect. Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large aircraft structural parts. The manufacturing of 7075 aluminum alloy structural parts by laser engineered net shaping technology has become an important development direction in the future aerospace field. Electrochemical corrosion resistance of aluminum alloys is of vital importance to improve reliability and life-span of lightweight components. A comparative study on microstructure and anti-corrosion performance of Al7075 alloy prepared by laser additive manufacturing and forging technology was conducted. There are hole defects in LENS-fabricated Al7075 alloy with uniformly distributed η phase. No defects are observed in Al7075 forgings. The large S phase particles and small ellipsoidal η phase particles are found in Al matrix. The corrosion mechanisms were revealed according to the analysis of polarization curves and corrosion morphology. It was found that compared with that prepared by forgings, the additive manufactured samples have lower corrosion tendency and higher corrosion rate. Corrosion occurred preferentially at the hole defects. The incomplete passivation film at the defects leads to the formation of a local cell composed of the internal Al, corrosion solution and the surrounding passive film, which further aggravates the corrosion.