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Acta Metall Sin  2018, Vol. 54 Issue (1): 100-108    DOI: 10.11900/0412.1961.2017.00203
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Effect of Non-Isothermal Retrogression and Re-Ageing on Microstructure and Properties of Al-8Zn-2Mg-2Cu Alloy Thick Plate
Di FENG1(), Xinming ZHANG2, Hongmei CHEN1, Yunxue JIN1, Guoying WANG1
1 School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
2 School of Materials Science and Engineering, Central South University, Changsha 410083, China
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Di FENG, Xinming ZHANG, Hongmei CHEN, Yunxue JIN, Guoying WANG. Effect of Non-Isothermal Retrogression and Re-Ageing on Microstructure and Properties of Al-8Zn-2Mg-2Cu Alloy Thick Plate. Acta Metall Sin, 2018, 54(1): 100-108.

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Abstract  

7000 series Al alloy has been widely used in aeronautical structural materials because of its high strength, high stress corrosion cracking resistance and good fatigue resistance when treated by retrogression and re-ageing (RRA). Al-8Zn-2Mg-2Cu (mass fraction, %) thick plate is supposed to manufacture the aircraft wing in Chinese big plane project. Due to the non-isothermal environment in the process of heat treatment for aluminum alloy thick plate, the influence of coupling effect of non-isothermal retrogression temperature field and time on the microstructure and properties of Al-8Zn-2Mg-2Cu alloy thick plate was investigated by the non-isothermal kinetic model, mechanical properties tests, electrical conductivity test and TEM observations. The results show that, the electrical conductivity increases while the hardness and strength decrease with the non-isothermal retrogression time increasing. The optimized non-isothermal retrogression and re-ageing (NRRA) treatment makes the size distribution range of MgZn2 phase wider. Therefore,the logical matching between the dislocation cutting off mechanism and the dislocation by-passing mechanism effectively reduces the loss of hardness. Meanwhile, the electrical conductivity is significantly improved. After the treatment of 105 ℃, 24 h (pre-ageing) and non-isothermal regression (120 min) with slow heating rate and 120 ℃, 24 h re-ageing, the Al-8Zn-2Mg-2Cu alloy thick plate possesses an excellent comprehensive performance than those of T6 and T73 states. The tensile strength, yield strength and electrical conductivity are 620 MPa, 593 MPa and 21.1 MS/m, respectively. The NRRA treatment with slow heating rate is more suitable for the ageing treatment of thick plate.
Key words:  Al-Zn-Mg-Cu alloy      thick plate      non-isothermal retrogression and re-ageing      ageing kinetics     
Received:  25 May 2017     
ZTFLH:  TG146.2  
Fund: Supported by National Basic Research Program of China (No.2012CB619500), Natural Science Foundation of Jiangsu Province (No.BK20160560), Natural Science Foundation for Colleges and Universities of Jiangsu Province (No.16KJB430010), Priority Academic Program Development of Jiangsu Higher Education Institutions
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Di FENG
Xinming ZHANG
Hongmei CHEN
Yunxue JIN
Guoying WANG

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https://www.ams.org.cn/EN/10.11900/0412.1961.2017.00203     OR     https://www.ams.org.cn/EN/Y2018/V54/I1/100

Fig.1  Schematic of non-isothermal retrogression of Al-8Zn-2Mg-2Cu alloy thick plate (WQ—water quenching, AQ—air cooling)
Treatment Pre-ageing Retrogression Re-ageing
NRRA-i 105 ℃, 24 h 5 ℃min-1 and 190 ℃, i min 120 ℃, 24 h
T6 120 ℃, 24 h - -
T73 120 ℃, 6 h - 160 ℃, 24 h
Table 1  Parameters of ageing treatment
Fig.2  Ageing temperature-time T(t) curves of Al-8Zn-2Mg-2Cu alloy 30 mm thick plate (retrogression stage)
Fig.3  Hardness and electrical conductivity of Al-8Zn-2Mg-2Cu alloy 30 mm thick plate under different ageing treatments
Fig.4  Tensile properties of Al-8Zn-2Mg-2Cu alloy thick plate under different ageing treatments (σb—tensile strength, σ0.2—yield strength)
Fig.5  Bright field TEM images and corresponding SAED patterns along [001]Al (insets) of precipitates in matrix of Al-8Zn-2Mg-2Cu alloy thick plate under the ageing treatments of T6 (a), T73 (b), NRRA-95 (c), NRRA-120 (d), NRRA-160 (e) and schematic diagram of the diffraction patterns (f)[19]
Fig.6  Bright field TEM images of precipitates in grain boundary of Al-8Zn-2Mg-2Cu alloy thick plate under the ageing treatments of T6 (a), T73 (b), NRRA-95 (c), NRRA-120 (d) and NRRA-160 (e)
Fig.7  Scheil integral (Sc) -time curve of central layer in Al-8Zn-2Mg-2Cu alloy thick plate
Fig.8  Size distribution cartogram of intragranular precipitates under different ageing treatments
[1] Paul A R, Zhang Y, Knight S.Heat treatment of 7xxx series aluminium alloys—Some recent developments[J]. Trans. Nonferrous Met. Soc. China, 2014, 24: 2003
[2] Zhang X M, Deng Y L, Zhang Y.Development of high strength aluminum alloys and processing techniques for the materials[J]. Acta Metall. Sin., 2015, 51: 257(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: 257)
[3] Grong ?, Shercliff H R.Microstructural modelling in metals processing[J]. Prog. Mater. Sci., 2002, 47: 163
[4] Hutchinson C R, Gouné M, Redja?mia. A Selecting non-isothermal heat treatment schedules for precipitation hardening systems: An example of coupled process-property optimization[J]. Acta Mater., 2007, 55: 213
[5] Jiang D M, Liu Y, Liang S, et al.The effects of non-isothermal aging on the strength and corrosion behavior of AlZnMgCu alloy[J]. J. Alloys Compd., 2016, 681: 57
[6] 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 Mater., 2010, 58: 4814
[7] Staley J T.Method and process of non-isothermal aging for aluminum alloys [P]. Durham US Pat, 0237113Al, 2007
[8] Li K, Zhang K, Yang L, et al.Investigation of non-isothermal aging process of 7085 aluminum alloy [A]. Proceedings of the 12th International Conference on Aluminium Alloys[C]. Yokohama: The Japan Institute of Light Metals, 2010: 2120
[9] Zhen L, Huang M, Liu M, et al.Effect of cooling method on the microstructure and properties of 7085 aluminum alloy during non-isothermal aging [A]. Proceedings of the 12th International Conference on Aluminium Alloys[C]. Yokohama: The Japan Institute of Light Metals, 2010: 481
[10] Jiang J T, Xiao W Q, Yang L, et al.Ageing behavior and stress corrosion cracking resistance of a non-isothermally aged Al-Zn-Mg-Cu alloy[J]. Mater. Sci. Eng., 2014, A605: 167
[11] Liu Y, Jiang D M, Li B Q, et al.Effect of cooling aging on microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy[J]. Mater. Des., 2014, 57: 79
[12] Liu Y, Jiang D M, Li B Q, et al.Heating aging behavior of Al-8.35Zn-2.5Mg-2.25Cu alloy[J]. Mater. Des., 2014, 60: 116
[13] Peng X Y, Guo Q, Liang X P, et al.Mechanical properties, corrosion behavior and microstructures of a non-isothermal ageing treated Al-Zn-Mg-Cu alloy[J]. Mater. Sci. Eng., 2017, A688: 146
[14] Koziel J, Blaz L, Wloch G, et al.Precipitation processes during non-isothermal aging of fine-grained AA2219[J]. J. Alloys Compd., 2016, 682: 468
[15] Cina B.Reducing the susceptibility of alloys, particularly aluminium alloys, to stress corrosion cracking [P].US Pat, 3856584, 1974
[16] Feng D, Zhang X M, Liu S D, et al.The effect of pre-ageing temperature and retrogression heating rate on the microstructure and properties of AA7055[J]. Mater. Sci. Eng., 2013, A588: 34
[17] Su R M, Qu Y D, Li D R.Pre-aging of retrogression and re-aging of spray formed 7075 alloy[J]. Acta Metall. Sin., 2014, 50: 863(苏睿明, 曲迎东, 李荣德. 喷射态7075合金回归再时效中预时效的研究[J]. 金属学报, 2014, 50: 863)
[18] Starink M J, Li X M.A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys[J]. Metall. Mater. Trans., 2003, 34A: 899
[19] Chen J Z.Ageing precipitation behavior and mechanical properties of AA7055 aluminum alloy [D]. Harbin: Harbin Institute of Technology, 2008(陈军洲. AA7055 铝合金的时效析出行为与力学性能 [D]. 哈尔滨: 哈尔滨工业大学, 2008)
[20] Feng D, Zhang X M, Liu S D, et al.Effect of pre-aging temperature and retrogression heating rate on microstructure and properties of 7150 alloy[J]. Chin. J. Nonferrous Met., 2013, 23: 1173(冯迪, 张新明, 刘胜胆等. 预时效温度及回归加热速率对7150铝合金显微组织及性能的影响[J]. 中国有色金属学报, 2013, 23: 1173)
[21] Ning A L, Liu Z Y, Feng C, et al.Analysis on the behavior of exceeding peak aging strength of aluminum alloy at condition of retrogression and reaging[J]. Acta Metall. Sin., 2006, 42: 1253(宁爱林, 刘志义, 冯春等. 铝合金回归再时效状态的超峰时效强度行为分析[J]. 金属学报, 2006, 42: 1253)
[22] Feng D, Zhang X M, Liu S D, et al.Non-isothermal retrogression kinetics for grain boundary precipitate of 7A55 aluminum alloy[J]. Trans. Nonferrous Met. Soc. China, 2014, 24: 2212
[23] Feng D, Zhang X M, Liu S D, et al.Non-isothermal “retrogression and re-ageing” treatment schedule for AA7055 thick plate[J]. Mater. Des., 2014, 60: 208
[24] Cui Z Q, Qin Y C.Metallography & Heat Treatment [M]. Beijing: Mechanical Industry Press, 2012: 179(崔忠圻, 覃耀春. 金属学与热处理 [M]. 北京: 机械工业出版社, 2012: 179)
[25] Lumley R.Fundamentals of Aluminium Metallurgy [M]. London: Woodhead Publishing Ltd., 2011: 356
[26] Cui X L, Wu Y Y, Zhang G J, et al.Study on the improvement of electrical conductivity and mechanical properties of low alloying electrical aluminum alloys[J]. Composites, 2017, 110B: 381
[27] Zhang G Y, Zhang H, Fang G L, et al.Electronic structure of different regions and analysis of stress corrosion mechanism of Al-Zn-Mg-Cu alloys[J]. Acta Metall. Sin., 2009, 45: 687(张国英, 张辉, 方戈亮等. Al-Zn-Mg-Cu系铝合金中不同区域电子结构及应力腐蚀机理分析[J]. 金属学报, 2009, 45: 687)
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