Effect of pre-treatment on microstructure and intergranular corrosion behavior of Al-Mg-Si alloy for automobile

doi:10.13251/j.issn.0254-6051.2022.02.015

Abstract

Abstract: Evolution laws of microstructure and intergranular corrosion behavior of the Al-Mg-Si alloy after bake hardening under different pre-treatment conditions were studied by tensile test, intergranular corrosion test, electrochemical test, metallographic microscope and transmission electron microscope. The results show that with the increase of pre-straining amount, the quantity density and size of grain boundary precipitates of the tested alloy decrease correspondingly, while the intragranular precipitates (β″ phase) increase in precipitation quantity and decrease in size, so that the tested alloy pre-treated differently has different comprehensive properties. The pre-treatment process composed of pre-straining and pre-aging is very beneficial to improve the comprehensive properties of Al-Mg-Si alloy, the intergranular corrosion resistance and bake hardening property are significantly improved, which is mainly attributed to the fact that the tested alloy do not form precipitation-free zone during bake hardening process, the grain boundary precipitates are less and discontinuous, and the matrix strengthening phase (β″ phase) is fully precipitated by consuming a large number of solute atoms.

Key words: Al-Mg-Si alloy, pre-straining, pre-aging, microstructure, intergranular corrosion

CLC Number:

TG178

Min Xudong, Huang Yuanchun, Xiao Zhengbing, Liu Yu, Ren Xianwei, Zou Ti. Effect of pre-treatment on microstructure and intergranular corrosion behavior of Al-Mg-Si alloy for automobile[J]. Heat Treatment of Metals, 2022, 47(2): 78-85.

References

[1]Ren X W, Huang Y C, Zhou W L, et al. Influence of pre-recovery on recrystallization behavior, microstructure and mechanical properties of twin-roll cast AA6016 sheet[J]. Materials Science and Engineering A, 2019, 764: 138-159.
[2]Aruga Y, Kozuka M, Takaki Y, et al. Effects of natural aging after pre-aging on clustering and bake-hardening behavior in an Al-Mg-Si alloy[J]. Scripta Materialia, 2016, 116: 82-86.
[3]Ding L P, He Y, Wen Z, et al. Optimization of the pre-aging treatment for an AA6022 alloy at various temperatures and holding times[J]. Journal of Alloys and Compounds, 2015, 647: 238-244.
[4]Yin D Y, Xiao Q, Chen Y Q, et al. Effect of natural ageing and pre-straining on the hardening behaviour and microstructural response during artificial ageing of an Al-Mg-Si-Cu alloy[J]. Materials and Design, 2016, 95: 329-339.
[5]Zhang H, Li L X, Yuan D, et al. Hot deformation behavior of the new Al-Mg-Si-Cu aluminum alloy during compression at elevated temperatures[J]. Materials Characterization, 2007, 58(2): 168-173.
[6]Birol Y. Pre-straining to improve the bake hardening response of a twin-roll cast Al-Mg-Si alloy[J]. Scripta Materialia, 2005, 52(3): 169-173.
[7]Jin S X, Ngai T W, Li L J, et al. Influence of natural aging and pre-treatment on the precipitation and age-hardening behavior of Al-1.0Mg-0.65Si-0.24Cu alloy[J]. Journal of Alloys and Compounds, 2018, 742: 852-859.
[8]Shen C H. Pre-treatment to improve the bake-hardening response in the naturally aged Al-Mg-Si alloy[J]. Journal of Materials Science and Technology, 2011, 27(3): 205-212.
[9]贺春林, 孟小丹, 马国峰, 等. 6000系铝合金晶间腐蚀研究进展[J]. 沈阳大学学报(自然科学版), 2014, 26(1): 18-23.
He Chunlin, Meng Xiaodan, Ma Guofeng, et al. Research development in intergranular corrosion of 6000-series aluminum alloys[J]. Journal of Shenyang University(Natural Science), 2014, 26(1): 18-23.
[10]Carle D, Blount G. The suitability of aluminium as an alternative material for car bodies[J]. Materials and Design, 1999, 20(5): 267-272.
[11]Tao G H, Liu C H, Chen J H, et al. The influence of Mg/Si ratio on the negative natural aging effect in Al-Mg-Si-Cu alloys[J]. Materials Science and Engineering A, 2015, 642: 241-248.
[12]Ravi C, Wolverton C. First-principles study of crystal structure and stability of Al-Mg-Si-(Cu) precipitates[J]. Acta Materialia, 2004, 52(14): 4213-4227.
[13]刘胜胆, 陈小连, 张端正, 等. 固溶温度对6082铝合金显微组织与性能的影响[J]. 中国有色金属学报, 2015, 25(3): 582-588.
Liu Shengdan, Chen Xiaolian, Zhang Duanzheng, et al. Effect of solution heat treatment temperature on microstructure and properties of 6082 aluminum alloy[J]. The Chinese Journal of Nonferrous Metals, 2015, 25(3): 582-588.
[14]Guo M X, Du J Q, Zheng C H, et al. Influence of Zn contents on precipitation and corrosion of Al-Mg-Si-Cu-Zn alloys for automotive applications[J]. Journal of Alloys and Compounds, 2019, 778: 256-270.
[15]Guan Q M, Sun J, Wang W Y, et al. Pitting corrosion of natural aged Al-Mg-Si extrusion profile[J]. Materials, 2019, 12(7): 1081-1096.
[16]Li J H, Li F G, Ma X K, et al. Effect of grain boundary characteristic on intergranular corrosion and mechanical properties of severely sheared Al-Zn-Mg-Cu alloy[J]. Materials Science and Engineering: A, 2018, 732: 53-62.