Effect of non-isothermal aging on microstructure and properties of 7003 aluminum alloy

doi:10.13251/j.issn.0254-6051.2020.02.028

Abstract

Abstract:

The precipitation and strengthening rules of 7003 aluminum alloy during non-isothermal aging (NIA) process were researched by combining TEM analysis and mechanical properties test. The corrosion resistance of the alloy was evaluated based on the test results of electrical conductivity, intergranular corrosion and electrochemical corrosion. The test results show that when heated to 180 ℃ at 20 ℃/h, the hardness and strength of the alloy reach their peak values of 113 HV0.5 and 367.8 MPa respectively, which is equivalent to the T6 standard. In the cooling stage in the temperature range of 180-160 ℃, the alloy can obtain higher strength and similar electrical conductivity comparing to the T74 condition. The corrosion resistance is continuously improved during the non-isothermal aging process. GP zones and η′ phases are the primary precipitates at the heating stage, while the GP zones gradually disappear and the η′ phase coarsens, and new fine precipitates are formed in the matrix grains. From the beginning of the heating to the end of the cooling, the number and size of the precipitated phases at the grain boundaries are getting larger and larger, and they are distributed intermittently along the grain boundaries. The width of precipitate free zones also increases steadily.

Key words: 7003 aluminum alloy, non-isothermal aging, mechanical properties, corrosion resistance, microstructure

CLC Number:

TG146.2

Yu Gang, Xiang Jianbo, Zhao Zhongxin, Luo Fenghua. Effect of non-isothermal aging on microstructure and properties of 7003 aluminum alloy[J]. HTM, 2020, 45(2): 143-148.

References

[1]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.
[2]毛杰, 熊京远, 王超, 等. 7003 铝合金双级双时效峰的显微组织与性能[J]. 热加工工艺, 2012, 41(16): 206-209.
Mao Jie, Xiong Jingyuan, Wang Chao, et al. Microstructure and properties of two stages double-peak aged in 7003 Al alloy[J]. Hot Working Technology, 2012, 41(16): 206-209.
[3]Dursun T, Soutis C. Recent developments in advanced aircraft aluminium alloys[J]. Materials and Design, 2014, 56: 862-871.
[4]Chen S, Chen K, Dong P, et al. Effect of recrystallization and heat treatment on strength and SCC of an Al-Zn-Mg-Cu alloy[J]. Journal of Alloys and Compounds, 2013, 581: 705-709.
[5]Song F, Zhang X, Liu S, et al. Exfoliation corrosion behavior of 7050-T6 aluminum alloy treated with various quench transfer time[J]. Transactions of Nonferrous Metals Society of China, 2014, 24(7): 2258-2265.
[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: 17-25.
[7]Peng G, Chen K, Chen S, et al. Influence of repetitious-RRA treatment on the strength and SCC resistance of Al-Zn-Mg-Cu alloy[J]. Materials Science and Engineering: A, 2011, 528(12): 4014-4018.
[8]Staley J. Method and process of non-isothermal aging for aluminum alloys: U. S. Patent Application 11/684, 939[P]. 2007-11-22.
[9]Jiang J T, Tang Q J, Yang L, et al. Non-isothermal ageing of an Al-8Zn-2Mg-2Cu alloy for enhanced properties[J]. Journal of Materials Processing Technology, 2016, 227: 110-116.
[10]Tsai T C, Chuang T H. Relationship between electrical conductivity and stress corrosion cracking susceptibility of Al 7075 and Al 7475 alloys[J]. Corrosion, 1996, 52(6): 414-416.
[11]Starink M J, Li X M. A model for the electrical conductivity of peak-aged and overaged Al-Zn-Mg-Cu alloys[J]. Metallurgical and Materials Transactions A, 2003, 34(4): 899-911.
[12]Liu X Y, Li M J, Gao F, et al. Effects of aging treatment on the intergranular corrosion behavior of Al-Cu-Mg-Ag alloy[J]. Journal of Alloys and Compounds, 2015, 639: 263-267.
[13]刘秀晨, 安成强, 崔作兴. 金属腐蚀学[M]. 北京: 国防工业出版社, 2002.
[14]Rout P K, Ghosh M M, Ghosh K S. Microstructural, mechanical and electrochemical behaviour of a 7017 Al-Zn-Mg alloy of different tempers[J]. Materials Characterization, 2015, 104: 49-60.
[15]Jiang X J, Tafto J, Noble B, et al. Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys[J]. Metallurgical and Materials Transactions A, 2000, 31(2): 339-348.
[16]Nicolas M, Deschamps A. Characterisation and modelling of precipitate evolution in an Al-Zn-Mg alloy during non-isothermal heat treatments[J]. Acta Materialia, 2003, 51(20): 6077-6094.
[17]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.
[18]刘炎. 7000 系铝合金的非等温时效行为及其对力学性能的影响[D]. 哈尔滨: 哈尔滨工业大学, 2014.
[19]Xiao Y P, Pan Q L, Li W B, et al. Influence of retrogression and re-aging treatment on corrosion behaviour of an Al-Zn-Mg-Cu alloy[J]. Materials and Design, 2011, 32(4): 2149-2156.
[20]Chen S, Chen K, Peng G, et al. Effect of heat treatment on strength, exfoliation corrosion and electrochemical behavior of 7085 aluminum alloy[J]. Materials and Design, 2012, 35: 93-98.
[21]Peng G S, Chen K H, Chen S Y, et al. Influence of dual-RRA temper on the exfoliation corrosion and electrochemical behavior of Al-Zn-Mg-Cu alloy[J]. Materials and Corrosion, 2013, 64(4): 284-289.