摘要
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 distributedηphase.No defects are observed in Al7075 forgings.The large S phase particles and small ellipsoidalηphase 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.
Al7075合金是一种典型的航空铝合金,具有良好的力学性能和阳极氧化效果。激光近净成形技术在高性能大型飞机结构件的整体成形中具有独特的优势。利用激光近净成形制造7075铝合金构件已成为未来航空航天领域的重要发展方向。铝合金的耐电化学腐蚀性能对提高轻量化构件的可靠性和寿命具有重要意义。本文对激光近净成形和锻造工艺制备的Al7075合金的组织和耐蚀性能进行了对比研究。发现激光近净成形制造的Al7075合金中存在孔隙缺陷,η相分布均匀。在Al7075锻件中未发现任何冶金缺陷,铝基体中存在较大的S相颗粒和较小的η相颗粒。随后,通过极化曲线和腐蚀形貌分析,揭示了不同工艺制造Al7075合金的腐耐腐蚀性能和腐蚀机理。与锻件相比,激光近净成形制备的试样具有较低的腐蚀倾向和较快的腐蚀速率。腐蚀优先发生在孔洞缺陷处。缺陷处的钝化膜不完整,形成了由铝、腐蚀溶液和周围钝化膜组成的局部电池,加剧了腐蚀。
作者
ZHANG Jin-liang
YE Jie-liang
SONG Bo
LI Rui-di
SHI Yu-sheng
张金良;叶界梁;宋波;李瑞迪;史玉升(State Key Laboratory of Materials Processing and Die&Mould Technology,School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China)
基金
Project(2016YFB1100101)supported by the National Key Research and Development Program of China。
