多级时效热处理对7056铝合金析出组织与耐蚀性的影响
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摘要
利用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、力学性能测试、电导率测试以及剥落腐蚀、慢应变速率拉伸应力腐蚀(SSRT)、Tafel循环极化曲线等手段研究多级时效热处理对7056铝合金析出组织及耐蚀性的影响。结果表明:过时效再时效热处理后溶质原子二次析出,晶内析出相体积分数增大,晶界析出相粗化断开,无沉淀析出带宽化。与120℃/24h相比,采用120℃/6h预时效工艺有利于晶内细小析出相回溶和粗大相长大。再时效热处理可提高过时效合金的强度和电导率,与峰时效和回归再时效相比,合金的抗拉强度损失不大,电导率明显提升。过时效再时效热处理后,合金晶界处连续阳极溶解被有效避免,抗剥落腐蚀和抗应力腐蚀性能增强。
The influence of different multi-stage aging heat treatment on microstructure and corrosion resistance of 7056 alloy was investigated by the measurements of transmission electron microscope(TEM), scanning electron microscope(SEM),mechanical properties and electrical conductivity, exfoliation corrosion, slow strain rate testing(SSRT), Tafel cyclic polarization. The results show that after over-aging and re-aging heat treatment, the solute atoms precipitate again, and the volume fraction of the precipitate in the matrix increases, the grain boundary precipitates coarsen and become discontinuous, the precipitate-free zone becomes wider. Compared with 120℃/24 h pre-aging,120℃/6 h has advantage in terms of dissolution of finer precipitates and the growth of large coarse phase. Re-aging heat treatment can improve the strength and conductivity of over-aging alloys;compared with peak aging and retrogression and re-aging, the loss of tensile strength of the alloy is not significant, while the conductivity increases obviously. After over-aging and re-aging heat treatment, continuous anodic dissolution is avoided effectively, and the exfoliation corrosion resistance and stress corrosion cracking is enhanced.
The influence of different multi-stage aging heat treatment on microstructure and corrosion resistance of 7056 alloy was investigated by the measurements of transmission electron microscope(TEM), scanning electron microscope(SEM),mechanical properties and electrical conductivity, exfoliation corrosion, slow strain rate testing(SSRT), Tafel cyclic polarization. The results show that after over-aging and re-aging heat treatment, the solute atoms precipitate again, and the volume fraction of the precipitate in the matrix increases, the grain boundary precipitates coarsen and become discontinuous, the precipitate-free zone becomes wider. Compared with 120℃/24 h pre-aging,120℃/6 h has advantage in terms of dissolution of finer precipitates and the growth of large coarse phase. Re-aging heat treatment can improve the strength and conductivity of over-aging alloys;compared with peak aging and retrogression and re-aging, the loss of tensile strength of the alloy is not significant, while the conductivity increases obviously. After over-aging and re-aging heat treatment, continuous anodic dissolution is avoided effectively, and the exfoliation corrosion resistance and stress corrosion cracking is enhanced.
引文
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[2] MA K,HU T,YANG H,et al.Coupling of dislocations and precipitates:impact on the mechanical behavior of ultrafine grained Al-Zn-Mg alloys[J].Acta Materialia,2016,103:153-164.
[3] CHEN S Y,CHEN K H,DONG P X,et al.Effect of recrysta-llization and heat treatment on strength and SCC of an Al-Zn-Mg-Cu alloy[J].Journal of Alloys and Compounds,2013,581:705-709.
[4] HEINZ A,HASZLER A,KEIDEL C,et al.Recent development in aluminium alloys for aerospace applications[J].Materials Science and Engineering:A,2000,280(1):102-107.
[5] 张新明,邓运来,张勇.高强铝合金的发展及其材料的制备加工技术[J].金属学报,2015,51(3):257-271.ZHANG X M,DENG Y L,ZHANG Y.Development of high strength aluminium alloys and processing techniques for the mate-rials[J].Acta Metallurgica Sinica,2015,51(3):257-271.
[6] SHI Y J,PAN Q L,LI M J,et al.Influence of alloyed Sc and Zr,and heat treatment on microstructures and stress corrosion cracking of Al-Zn-Mg-Cu alloys[J].Materials Science and Engin-eering:A,2015,621:173-181.
[7] 李文婷,王浩伟,余军,等.铈离子对高强铝合金应力腐蚀开裂的缓蚀作用[J].材料工程,2017,45(5):20-30.LI W T,WANG H W,YU J,et al.Inhibition of Ce3+ on stress corrosion crack of high strength aluminum alloy[J].Journal of Materials Engineering,2017,45(5):20-30.
[8] 何正林,高文理,陆政,等.热处理对7A85铝合金组织和性能的影响[J].材料工程,2015,43(8):13-18.HE Z L,GAO W L,LU Z,et al.Effects of heat treatment on microstructure and properties of 7A85 aluminium alloy[J].Jour-nal of Materials Engineering,2015,43(8):13-18.
[9] MARLAUD T,DESCHAMPS A,BLEY F,et al.Evolution of precipitate microstructures during the retrogression and re-ageing heat treatment of an Al-Zn-Mg-Cu alloy[J].Acta Materialia,2010,58(14):4814-4826.
[10] 刘维,陈康华,陈送义,等.再时效对过时效7B50合金力学及腐蚀性能的影响[J].中南大学学报(自然科学版),2016,47(8):2600-2607.LIU W,CHEN K H,CHEN S Y,et al.Effect of re-aging on mechanical and corrosion properties of over-aging 7B50 alloy[J].Journal of Central South University (Science and Technology),2016,47(8):2600-2607.
[11] 陈康华,董朋轩,肖代红,等.一种Al-Zn-Mg-Cu系铝合金的时效热处理方法:CN103409710A[P].2013-11-27.CHEN K H,DONG P X,XIAO D H,et al.A kind of a aging treatment of Al-Zn-Mg-Cu series aluminium alloy:CN103409-710A[P].2013-11-27.
[12] 蒋建辉,郑子樵,唐娟,等.单级时效7056铝合金的显微组织与性能[J].机械工程材料,2013,37(4):69-74.JIANG J H,ZHENG Z Q,TANG J,et al.Microstructure and properties of single-aging 7056 aluminum alloy[J].Materials for Mechanical Engineering,2013,37(4):69-74.
[13] 蒋建辉.7056铝合金热处理工艺与组织性能研究[D].长沙:中南大学,2012.JIANG J H.The study of heating treatments and microstructures of 7056 aluminium alloy[D].Changsha:Central South Univer-sity,2012.
[14] 马灿,谭澄宇,覃思思,等.时效对7056铝合金在EXCO溶液中剥落腐蚀行为的影响[J].腐蚀与防护,2016,37(2):93-99.MA C,TAN C Y,QIN S S,et al.Effect of aging on exfoliation corrosion behavior of 7056 alloy in EXCO solution[J].Corrosion and Protection,2016,37(2):93-99.
[15] WEN K,FAN Y Q,WANG G J,et al.Aging behavior and precipitate characterization of a high Zn-containing Al-Zn-Mg-Cu alloy with various tempers[J].Materials & Design,2016,101:16-23.
[16] WEN K,FAN Y Q,WANG G J,et al.Aging behavior and fatigue crack propagation of high Zn-containing Al-Zn-Mg-Cu alloys with zinc variation[J].Progress in Natural Science:Materials International,2017,27(2):217-227.
[17] LIU J,KERSKER M M.Heat treatment of precipitation hardening alloys:US5108520[P].1992-04-28.
[18] 杨荣先,刘志义,陈来,等.回归再时效对超高强铝合金力学性能及组织的影响[J].粉末冶金材料科学与工程,2016,21(2):264-269.YANG R X,LIU Z Y,CHEN L,et al.Effect of RRA treatment on the mechanical properties and microstructure of ultrahigh strength aluminum alloys[J].Materials Science and Engineering of Powder Metallurgy,2016,21(2):264-269.
[19] 辛星.回归再时效中预时效对7050铝合金热轧板抗腐蚀性能的影响[D].长沙:中南大学,2013.XIN X.Effect of pre-aging in RRA on corrosion resistance of 7050 aluminum alloy hot-rolled plates[D].Changsha:Central South University,2013.
[20] 韩念梅,张新明,刘胜胆,等.回归再时效对7050铝合金强度和断裂韧性的影响[J].中国有色金属学报,2012,22(7):1871-1882.HAN N M,ZHANG X M,LIU S D,et al.Effects of retrogr-ession and reaging on strength and fracture toughness of alumin-um alloy 7050[J].The Chinese Journal of Nonferrous Metals,2012,22(7):1871-1882.
[21] 李文斌,潘清林,邹亮,等.含Sc的超高强Al-Zn-Cu-Mg-Zr合金的晶间腐蚀和剥落腐蚀行为[J].航空材料学报,2008,28(1):53-58.LI W B,PAN Q L,ZOU L,et al.Intergranular and exfoliation corrosion behaviour of high strength Al-Zn-Cu-Mg-Zr alloy containing Sc[J].Journal of Aeronautical Materials,2008,28(1):53-58.
[22] MUKHOPADHYAY A K,PRASAD K S,KUMAR V,et al.Key microstructural features responsible for improved stress corrosion cracking resistance and weldability in 7xxx series Al alloys containing micro/trace alloying additions[J].Materials Science Forum,2006,519/521:315-320.
[23] PENG G S,CHEN K H,CHEN S Y,et al.Influence of dual retrogression and re-aging temper on microstructure,strength and exfoliation corrosion behavior of Al-Zn-Mg-Cu alloy[J].Transactions of Nonferrous Metals Society of China,2012,22(4):803-809.