高能缺陷和第二相对新型超高强铝合金腐蚀行为的影响
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摘要
采用等径角挤压(ECAP)和固溶时效处理获得超高强铝合金,并采用透射电子显微镜、扫描电镜以及电化学工作站等测试手段对其微观结构演变以及电化学腐蚀行为进行研究。结果表明:等径角挤压变形后晶粒细化至亚微米(9.68→1μm),大变形诱导的溶质原子偏析和不连续脱溶效应造成第二相长大(53→416 nm)和晶界偏聚;大塑性变形材料经固溶时效处理后,部分第二相的晶界偏析现象减弱,呈细小颗粒状弥散分布于铝基体中。细晶组织和高能缺陷有利于形成附着力良好且致密稳定的氧化膜,晶界偏析的减弱和弥散细小的第二相抑制了点蚀对晶间腐蚀的促进作用,最终显著优化超高强铝合金的耐腐蚀性能。
Ultrahigh strength aluminum alloys were prepared by equal channel angular pressing(ECAP) and solution aging treatment. The microstructure evolution and electrochemical corrosion behavior of the alloy were studied by transmission electron microscopy(TEM), scanning electron microscopy(SEM) and electrochemical workstation. The results show that grains are refined to submicron level after ECAP. Solute segregation and discontinuous dissolution caused by severe plastic deformation lead to the coarsening of secondary phases particles and segregation at grain boundary. Partial secondary phase particles in Al-Zn-Mg-Cu alloy are refined and dispersed in aluminum matrix after the process of severe plastic deformation and solution aging, which demonstrates the decrease of secondary phase segregation at grain boundary. The dense and stable oxide films, as well as the fine secondary phase particles with diffused distribution, have beneficial influence on the improvement of corrosion resistance of ultra-high strength aluminum alloy. The dense and stable oxide films with high adhesion are formed by fine grain structure and high energy defects. Intergranular corrosion is depressed by dispersed fine secondary phase and decrease of grain boundary segregation.
Ultrahigh strength aluminum alloys were prepared by equal channel angular pressing(ECAP) and solution aging treatment. The microstructure evolution and electrochemical corrosion behavior of the alloy were studied by transmission electron microscopy(TEM), scanning electron microscopy(SEM) and electrochemical workstation. The results show that grains are refined to submicron level after ECAP. Solute segregation and discontinuous dissolution caused by severe plastic deformation lead to the coarsening of secondary phases particles and segregation at grain boundary. Partial secondary phase particles in Al-Zn-Mg-Cu alloy are refined and dispersed in aluminum matrix after the process of severe plastic deformation and solution aging, which demonstrates the decrease of secondary phase segregation at grain boundary. The dense and stable oxide films, as well as the fine secondary phase particles with diffused distribution, have beneficial influence on the improvement of corrosion resistance of ultra-high strength aluminum alloy. The dense and stable oxide films with high adhesion are formed by fine grain structure and high energy defects. Intergranular corrosion is depressed by dispersed fine secondary phase and decrease of grain boundary segregation.
引文
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[2]贺俊光,文九巴,周旭东.第二相对Al-Zn-Sn-Ga-Mg合金腐蚀行为的影响[J].中国有色金属学报,2013,23(3):628-634.HE Jun-guang,WEN Jiu-ba,ZHOU Xu-dong.Effect of corrosion behavior of second relative Al-Zn-Sn-Ga-Mg alloy[J].The Chinese Journal of Nonferrous Metals,2013,23(3):628-634.
[3]刘贵立,方戈亮.Al-Zn-Mg-Cu超高强铝合金晶界偏聚与腐蚀机制研究[J].稀有金属材料与工程,2009,38(9):1598-1601.LIU Gui-li,FANG Ge-liang.Study on grain boundary segregation and corrosion mechanism of Al-Zn-Mg-Cu ultra high strength aluminum alloy[J].Rare Metal Materials and Engineering,2009,38(9):1598-1601.
[4]王素梅,孙康宁,刘睿,毕见强.第二相粒子对ECAP挤压的2A12铝合金晶粒细化的影响[J].材料科学与工艺,2007,15(1):115-117.WANG Su-mei,SUN Kang-ning,LIU Rui,BI Jian-qiang.Effect of second phase particles on grain refinement of 2A12aluminum alloy extruded by ECAP[J].Materials Science and Technology,2007,15(1):115-117.
[5]赵鸿金,胡玉军,旷军平,杨泰胜.等通道角挤压第二相状态研究进展[J].热加工工艺,2015,44(11):9-12.ZHAO Hong-jin,HU Yu-jun,KUANG Jun-ping,YANGTai-sheng.Research progress of second phase state in equal channel angle extrusion[J].Hot Working Technology,2015,44(11):9-12.
[6]BRUNNER J G,BIRBILIS N,RALSTON K D,VIRTANEN S.Impact of ultrafine-grained microstructure on the corrosion of aluminium alloy AA2024[J].Corrosion Science,2012,57:209-214.
[7]HOCKAUF M,MEYER L W,NICKEL D,ALISCH G,LAMPKE T,WIELAGE B,KRUGER L.Mechanical properties and corrosion behaviour of ultrafine grained AA6082 produced by equal-channel angular pressing[J].Journal of Materials Science,2008,43(23/24):7409-7417.
[8]PANG J J,LIU F C,LIU J,TAN M J,BLACKWOOD D J.Friction stir processing of aluminium alloy AA7075:Microstructure,surface chemistry and corrosion resistance[J].Corrosion Science,2016,106:217-228.
[9]RALSTON K D,FABIJANIC D,BIRBILIS N.Effect of grain size on corrosion of high purity aluminium[J].Electrochimica Acta,2011,56(4):1729-1736.
[10]SAUVAGE X,WETSCHER F,PAREIGE P.Mechanical alloying of Cu and Fe induced by severe plastic deformation of a Cu-Fe composite[J].Acta Materialia,2005,53(7):2127-2135.
[11]SU L H,LU C,HE L Z,ZHANG L C,GUAGLIARDO P,TIEU A K,SAMARIN S N,WILLIAMS J F,LI H J.Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures[J].Acta Materialia,2012,60(10):4218-4228.
[12]SAUVAGE X,WILDE G,DIVINSKI S V,HORITA Z,VALIEV R Z.Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena[J].Materials Science and Engineering A,2012,540:1-12.
[13]SAUVAGE X,MURASHKIN M Y,VALIEV R Z.Atomic scale investigation of dynamic precipitation and grain boundary segregation in a 6061 aluminium alloy nanostructured by ECAP[J].Kovove Materialy,2011,49(1):11-15.
[14]CERRI E,LEO P.Influence of severe plastic deformation on aging of Al-Mg-Si alloys[J].Materials Science and Engineering A,2005,s410/411:226-229.
[15]CHEN Y,GAO N,SHA G,RINGER S P,STARINK M J.Strengthening of an Al-Cu-Mg alloy processed by high-pressure torsion due to clusters,defects and defect-cluster complexes[J].Materials Science and Engineering A,2015,627:10-20.
[16]RALSTON K D,BIRBILIS N,DAVIES C H J.Revealing the relationship between grain size and corrosion rate of metals[J].Scripta Mater,2010,63:1201-1204.
[17]DONG Chao-fang,XIAO Kui,XU Lin,SHENG Hai,ANYing-hui,LI Xiao-gang.Characterization of 7A04 aluminum alloy corrosion under atmosphere with chloride Ions using electrochemical techniques[J].Rare Metal Materials and Engineering,2011,40(S2):275-279.
[18]CHEN Y,GAO N,SHA G,RINGER S P,STARINK M J.Microstructural evolution,strengthening and thermal stability of an ultrafine-grained Al-Cu-Mg alloy[J].Acta Materialia,2016,109:202-212.
[19]WANG X,NIE M Y,WANG C T,WANG S C,GAO N.Microhardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion[J].Materials&Design,2015,83:193-202.
[20]BUCHHEIT R G,MORAN J P,STONER G E.Electrochemical behavior of the T1(Al2Cu Li)intermetallic compound and its role in localized corrosion of Al-2%Li-3%Cu alloys[J].Corrosion,1994,50:120-130.
[21]LI X Z,HANSEN V,GJ?NNES J,WALLENBERG L R.HREM study and structure modeling of theη′phase,the hardening precipitates in commercial Al-Zn-Mg alloys[J].Acta Materialia,1999,47(9):2651-2659.