基于正交试验的7085铝合金双级时效制度
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摘要
采用正交试验,研究7085铝合金双级时效的预时效时间、二级时效温度和时间3个因素对硬度和电导率的影响,运用方差分析法研究3个影响因素的显著性,采用室温拉伸、慢应变速率拉伸和透射电镜观察等方法研究二级时效温度和时间对7085铝合金组织性能的影响。研究结果表明:3个因素的显著性从大到小为二级时效温度、二级时效时间、预时效时间。二级时效温度的提高和时间的延长使晶内η′相转变为η相、晶界相粗化且不连续,导致合金强度降低、抗应力腐蚀性能大幅提高,其中温度的影响作用更为显著,与正交试验结果相符。该合金最佳的T76双级时效工艺为:121℃/5 h+163℃/12 h,其抗拉强度和屈服强度分别为530 MPa和483 MPa,伸长率为14.2%,电导率为22.9 MS/m。
The effect of pre-aging time, secondary aging temperature and time of two-step aging on hardness and conductivity of 7085 aluminum alloy was investigated by orthogonal experiment. The significant regularity was studied by variance analysis, and the influence of secondary aging temperature and time on microstructure and properties of 7085 aluminum alloy was investigated by means of tensile test, slow strain rate test(SSRT) and transmission electron microscopy(TEM). The results show that the significant regularity(from big to small) of three factors is secondary aging temperature, secondary aging time, pre-aging time η′ phase transforms to η phase gradually, grain boundary precipitates become coarse and tend to be discontinuous with the increase of the secondary aging temperature and time. Thus, the strength of alloys decreases while the stress corrosion cracking(SCC) resistance increases. The influence of secondary aging temperature is more significant. During the optimal two-step aging treatment of 121 ℃/5 h+163 ℃/12 h, the tensile strength, yield strength, elongation and conductivity of the alloy are 530 MPa, 483 MPa, 12.6%, 22.9 MS/m, respectively.
The effect of pre-aging time, secondary aging temperature and time of two-step aging on hardness and conductivity of 7085 aluminum alloy was investigated by orthogonal experiment. The significant regularity was studied by variance analysis, and the influence of secondary aging temperature and time on microstructure and properties of 7085 aluminum alloy was investigated by means of tensile test, slow strain rate test(SSRT) and transmission electron microscopy(TEM). The results show that the significant regularity(from big to small) of three factors is secondary aging temperature, secondary aging time, pre-aging time η′ phase transforms to η phase gradually, grain boundary precipitates become coarse and tend to be discontinuous with the increase of the secondary aging temperature and time. Thus, the strength of alloys decreases while the stress corrosion cracking(SCC) resistance increases. The influence of secondary aging temperature is more significant. During the optimal two-step aging treatment of 121 ℃/5 h+163 ℃/12 h, the tensile strength, yield strength, elongation and conductivity of the alloy are 530 MPa, 483 MPa, 12.6%, 22.9 MS/m, respectively.
引文
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[21]NAJJAR D,MAGNIN T,WARNER T J.Influence of critical surface defects and localized competition between anodic dissolution and hydrogen effects during stress corrosion cracking of a 7050 aluminum alloy[J].Materials Science and Engineering A,1997,238(2):293-302.
[22]李波,潘清林,李晨,等.时效处理对含钪Al-Zn-Mg-Zr合金腐蚀行为的影响[J].中南大学学报(自然科学版),2013,44(10):3998-4005.LI Bo,PAN Qinglin,LI Chen,et al.Influence of aging treatment on corrosion behavior of Al-Zn-Mg-Zr alloy with Sc element[J].Journal of Central South University(Science and Technology),2013,44(10):3998-4005.
[2]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 Xinming,DENG Yunlai,ZHANG Yong.Development of high strength aluminum alloys and processing techniques for the materials[J].Acta Metallurgica Sinica,2015,51(3):257-271.
[3]HEINZ A,HASZLER A,KEIDEL C,et al.Recent development in aluminum alloys for aerospace applications[J].Materials Science and Engineering A,2000,280(3):102-107.
[4]WALLANDE W,BEDDOES J C,MALHERBE M C.A new approach to the problem of stress corrosion cracking in 7075-T6aluminum[J].Canadian Aeronautics and Space Journal,1981,27(3):222-232.
[5]MARLAUD T,DESCHAMPS A,BLEY F,et al.Influence of alloy composition and heat treatment on precipitate composition in Al-Zn-Mg-Cu alloys[J].Acta Materialia,2010,58(1):248-260.
[6]XU D K,BIRBILIS N,ROMETSCH P A.The effect of pre-ageing temperature and retrogression heating rate on the strength and corrosion behaviour of AA7150[J].Corrosion Science,2012,54(1):17-25.
[7]田福泉,李念奎,崔建忠.超高强铝合金强韧化的发展过程及方向[J].轻合金加工技术,2005,33(12):1-9.TIAN Fuquan,LI Niankui,CUI Jianzhong.Research and development of ultra high strength aluminum alloys[J].Light Alloy Fabrication Technology,2005,33(12):1-9.
[8]OLIVEIRA A F,BARROS M C,CARDOSO K R,et al.The effect of RRA on the strength and SCC resistance on AA7050and AA7150 aluminum alloys[J].Materials Science and Engineering A,2004,379(1/2):321-326.
[9]LIU Yingying,XIA Changqing,PENG Xiaomin,et al.Effect of heat treatment on microstructures and mechanical properties of Al-6Zn-2Mg-1.5Cu-0.4Er alloy[J].Journal of Central South University of Technology,2010,17(1):24-27.
[10]冯春,刘志义,宁爱林,等.超高强铝合金RRA热处理工艺的研究进展[J].材料导报,2006,20(4):98-101.FENG Chun,LIU Zhiyi,NING Ailin,et al,Research and progress in retrogression and reaging treatment of super-high strength aluminum alloy[J].Materials Review,2006,20(4):98-101.
[11]田福泉,崔建忠.双级时效对7050铝合金组织和性能的影响[J].中国有色金属学报,2006,16(6):958-963.TIAN Fuquan,CUI Jianzhong.Effect of duplex aging on microstructure and properties of 7050 aluminum alloy[J].The Chinese Journal of Nonferrous Metals,2006,16(6):958-963.
[12]张新明,宋丰轩,刘胜胆,等.双级时效对7050铝合金板材剥蚀性能的影响[J].中南大学学报(自然科学版),2011,42(8):2252-2259.ZHANG Xinming,SONG Fengxuan,LIU Shengdan,et al.Influence of two-step aging on exfoliation corrosion properties of 7050 aluminum alloy plate[J].Journal of Central South University(Science and Technology),2011,42(8):2252-2259.
[13]闫焱,郑子樵,龙佳.7A55铝合金预拉伸板材的双级时效工艺[J].材料热处理学报,2010,31(11):128-133.YAN Yan,ZHENG Ziqiao,LONG Jia.Double aging studying of pre-stretched 7A55 aluminum alloy plate[J].Transactions of Materials and Heat Treatment,2010,31(11):128-133.
[14]刘瑞江,张业旺,闻崇炜,等.正交试验设计和分析方法研究[J].实验技术与管理,2010(9):52-55.LIU Ruijiang,ZHANG Yewang,WEN Chongwei,et al.Study on the design and analysis methods of orthogonal experiment[J].Experimental Technology and Management,2010(9):52-55.
[15]AMS4329A,Aluminum alloy,plate(7085-T7651)7.5Zn-1.6Cu-1.5Mg-0.12Zr solution heat treated,stress-relieved,and overaged[S].
[16]SONG R G,DIETZEL W,ZHANG B J,et al.Stress corrosion cracking and hydrogen embrittlement of an Al-Zn-Mg-Cu alloy[J].Acta Materialia,2004,52(16):4727-4743.
[17]黎彦希,陈康华,陈送义,等.添加Cr和Yb对Al-Zn-Mg-x Cu-Zr超强铝合金组织与性能的影响[J].中南大学学报(自然科学版),2015,46(12):4422-4433.LI Yanxi,CHEN Kanghua,CHEN Songyi,et al.Effect of Cr and Yb additions on microstructure and properties of Al-Zn-Mg-x Cu-Zr alloy[J].Journal of Central South University(Science and Technology),2015,46(12):4422-4433.
[18]MARLAUD T,DESCHAMPS A,BLEY F,et al.Influence of alloy composition and heat treatment on precipitate composition in Al-Zn-Mg-Cu alloys[J].Acta Materialia,2010,58(1):248-260.
[19]SHARMA M M,AMATEAU M F,EDEN T J.Hardening mechanisms of spray formed Al-Zn-Mg-Cu alloys with scandium and other elemental additions[J].Journal of Alloys and Compounds,2006,416(1/2):135-142.
[20]COOPER K R,KELLY R G.Crack tip chemistry and electrochemistry of environmental cracks in AA 7050[J].Corrosion Science,2007,49(6):2636-2662.
[21]NAJJAR D,MAGNIN T,WARNER T J.Influence of critical surface defects and localized competition between anodic dissolution and hydrogen effects during stress corrosion cracking of a 7050 aluminum alloy[J].Materials Science and Engineering A,1997,238(2):293-302.
[22]李波,潘清林,李晨,等.时效处理对含钪Al-Zn-Mg-Zr合金腐蚀行为的影响[J].中南大学学报(自然科学版),2013,44(10):3998-4005.LI Bo,PAN Qinglin,LI Chen,et al.Influence of aging treatment on corrosion behavior of Al-Zn-Mg-Zr alloy with Sc element[J].Journal of Central South University(Science and Technology),2013,44(10):3998-4005.