Improved Properties in Relation to Fine Precipitate Microstructures Tailored by Combinatorial Processes in an Al-Cu-Mg-Si Alloy

doi:10.1007/s40195-020-01093-1

Abstract

Abstract:

The 2xxx series Al alloys have been widely used in aerospace industry owing to their high strength, good plasticity and superior formability. To ensure a good control of shape, the quenched alloy sheets require a small pre-deformation before artificial aging. However, this pre-deformation considerably deteriorates the mechanical strength of the Al-3.0Cu-1.8Mg-0.5Si (wt%) alloys due to the formation of unfavorable large-sized precipitates at dislocations. To tackle this issue, we designed a pre-aging process prior to the pre-deformation. The thermal-mechanical treatment, involving pre-aging, pre-deformation and subsequent aging, markedly enhanced the ultimate tensile strength up to 521 MPa compared to that (448 MPa) of the alloy without pre-aging. Microstructure characterization revealed that the fine precipitates (~ 2 nm) with a uniform dispersion were promoted within the Al matrix, which in turn partly suppressed the formation of the unfavorable large-sized precipitate (~ 100 nm). Our findings provide a new clue for designing stronger Al alloys with age-hardenability.

Key words: Aluminum alloys, Thermo-mechanical treatment, Precipitation, Age-hardenability

Fengjiao Niu, Jianghua Chen, Cuilan Wu, Jing Wu, Xiandong Xu, Pan Xie, Xiongwei Yu. Improved Properties in Relation to Fine Precipitate Microstructures Tailored by Combinatorial Processes in an Al-Cu-Mg-Si Alloy[J]. Acta Metallurgica Sinica (English Letters), 2020, 33(11): 1527-1534.

Figures/Tables 8

Table 1 Detailed process of the heat treatments used in this article

Heat treatment	Detailed process
T6	ST + WQ + AA at 180 °C
T8	ST + WQ + 6% CR + AA at 180 °C
NA7d-TMT	ST + WQ + NA for 7 days + 6% CR + AA at 180 °C
AA1h-TMT	ST + WQ + AA at 200 °C for 1 h + 6% CR + AA at 180 °C

Fig. 1 a Hardness-time curves of the Al-3.0Cu-1.8Mg-0.5Si alloy pre-aged at RT and 200 °C, and samples marked with arrows are selected to undergo the TMT processes, b Vickers hardness plotted against aging time curves of the samples treated by T6, T8 temper and TMT processes aging at 180 °C

Fig. 2 HAADF-STEM images of the peak-aged samples treated by T6 temper a, b, T8 temper c, d

Table 2 Mechanical properties of the peak-aged samples with different heat treatments

Heat treatment	Peak-aging time (h)	Peak hardness (HV)	σ_0.2 (MPa)	σ_b (MPa)	ε (%)
T6	48	153	411	469	9.9
T8	18	140	429	448	7.8
AA1h-TMT	9	157	454	500	7.3
NA7d-TMT	24	163	485	521	8.3

Fig. 3 Bright-field TEM image a and HAADF-STEM image b of the samples pre-aged at 200 °C for 1 h. The inset in b showing the structure of a precursor

Fig. 4 HAADF-STEM images of the peak-aged samples treated by AA1h-TMT process a-c and NA7d-TMT process d-f viewed along the [001]Al direction

Fig. 5 Low-magnification HAADF-STEM images of the peak-aged samples treated by T8 temper a, b, AA1h-TMT process, c, d, NA7d-TMT process, e, f viewed along the [001]Al direction

Table 3 Precipitates of the peak-aged samples with different heat treatments

Heat treatment	Main precipitates
Heat treatment	Dislocation-induced precipitates	Dislocation-free precipitates
T6	-	Si-modified GPB zones
T8	The coarse CPs (~ 100 nm)	Si-modified GPB zones
AA1h-TMT	A small amount of CPs (~ 50 nm)	A large amount of Si-modified GPB zones
NA7d-TMT	A small amount of CPs (~ 50 nm), some rod-like S phase	A large amount of Si-modified GPB zones

References 41

[1]	J.C. Williams, E.A. Starke, Acta Mater. 51, 5775(2003) DOI URL
[2]	S. Bai, Z. Liu, P. Ying, J. Wang, A. Wang, J. Alloys Compd. 725, 1288(2017) DOI URL
[3]	Y.L. Zhao, Z.Q. Yang, Z. Zhang, G.Y. Su, X.L. Ma, Acta Mater. 61, 1624(2013) DOI URL
[4]	X.W. Yu, J.H. Chen, J.Y. Li, C.L. Wu, X.B. Yang, Mater. Charact. 158, 110005(2019) DOI URL
[5]	S.P. Ringer, B.C. Muddle, I.J. Polmear, Metall. Mater. Trans. A 26, 1659 (1995) DOI URL
[6]	N. Unlu, B.M. Gable, G.J. Shiflet, E.A. Starke, Metall. Mater. Trans. A 34, 2757 (2003) DOI URL
[7]	R. Ferragut, A. Somoza, A. Tolley, Mater. Sci. Forum 363-365, 80(2001)
[8]	I.S. Zuiko, M.R. Gazizov, R.O. Kaibyshev, Phys. Met. Metallogr. 117, 906(2016) DOI URL
[9]	M. Gazizov, R. Kaibyshev, Mater. Sci. Eng. A 625, 119 (2015) DOI URL
[10]	J.F. Li, Z.H. Ye, D.Y. Liu, Y.L. Chen, X.H. Zhang, X.Z. Xu, Z.Q. Zheng, Acta Metall. Sin. Engl. Lett. 30, 133(2016)
[11]	N. Han, X. Zhang, S. Liu, B. Ke, X. Xin, Mater. Sci. Eng. A 528, 3714 (2011) DOI URL
[12]	Y.H. Zhao, X.Z. Liao, Z. Jin, R.Z. Valiev, Y.T. Zhu, Acta Mater. 52, 4589(2004) DOI URL
[13]	Y.H. Zhao, X.Z. Liao, S. Cheng, E. Ma, Y.T. Zhu, Adv. Mater. 18, 2280(2006)
[14]	Y.X. Lai, W. Fan, M.J. Yin, C.L. Wu, J.H. Chen, J. Mater. Sci. Technol. 41, 127(2020)
[15]	K. Teichmann, C.D. Marioara, S.J. Andersen, K. Marthinsen, Metall. Mater. Trans. A 43, 4006 (2012) DOI URL
[16]	C.R. Hutchinson, S.P. Ringer, Metall. Mater. Trans. A 31, 2721 (2000) DOI URL
[17]	F.J. Niu, J.H. Chen, S.Y. Duan, W.Q. Ming, J.B. Lu, C.L. Wu, Z. Le, J. Alloys Compd. 823, 153831(2020) DOI URL
[18]	C.H. Liu, X.L. Li, S.H. Wang, J.H. Chen, Q. Teng, J. Chen, Y. Gu, Mater. Des. 54, 144(2014) DOI URL
[19]	S.H. Wang, C.H. Liu, J.H. Chen, X.L. Li, D.H. Zhu, G.H. Tao, Mater. Sci. Eng. A 585, 233 (2013) DOI URL
[20]	J. Ren, Z. Chen, J. Peng, W. Ma, S.P. Ringer, J. Alloys Compd. 764, 679(2018) DOI URL
[21]	Z. Wang, H. Li, F. Miao, B. Fang, R. Song, Z. Zheng, Mater. Sci. Eng. A 607, 313 (2014) DOI URL
[22]	M. Weiss, A.S. Taylor, P.D. Hodgson, N. Stanford, Acta Mater. 61, 5278(2013) DOI URL
[23]	E. Thronsen, C.D. Marioara, J.K. Sunde, K. Minakuchi, T. Katsumi, I. Erga, S.J. Andersen, J. Friis, K. Marthinsen, K. Matsuda, R. Holmestad, Mater. Des. 186, 108203(2020) DOI URL
[24]	S. Bai, X. Yi, Z. Liu, J. Wang, J. Zhao, P. Ying, J. Alloys Compd. 764, 62(2018) DOI URL
[25]	X.B. Yang, J. Liu, J. Chen, C. Wan, L. Fang, P. Liu, C. Wu, Acta Metall. Sin. Engl. Lett. 27, 1070(2014)
[26]	J.F. Nie, B.C. Muddle, Acta Mater. 56, 3490(2008) DOI URL
[27]	L. Liu, J.H. Chen, S.B. Wang, C.H. Liu, S.S. Yang, C.L. Wu, Mater. Sci. Eng. A 606, 187 (2014) DOI URL
[28]	Z. Feng, Y. Yang, B. Huang, M. Han, X. Luo, J. Ru, Mater. Sci. Eng. A 528, 111 (2010)
[29]	S.C. Wang, M.J. Starink, Acta Mater. 55, 933(2007) DOI URL
[30]	B.I. Rodgers, P.B. Prangnell, Acta Mater. 108, 55(2016) DOI URL
[31]	C. Wolverton, Acta Mater. 55, 5867(2007) DOI URL
[32]	B. Klobes, K. Maier, T.E.M. Staab, Mater. Sci. Eng. A 528, 3253 (2011) DOI URL
[33]	L. Cao, P.A. Rometsch, M.J. Couper, Mater. Sci. Eng. A 559, 257 (2013) DOI URL
[34]	C. Li, G. Sha, J. Xia, Y. Liu, S.P. Ringer, Mater. Chem. Phys. 193, 421(2017) DOI URL
[35]	Z. Zhang, H. Xu, S. Wu, Y. Liu, Acta Metall. Sin. Engl. Lett. 26, 340(2013)
[36]	K. Misumi, K. Kaneko, T. Nishiyama, T. Maeda, K. Yamada, K.I. Ikeda, M. Kikuchi, K. Takata, M. Saga, K. Ushioda, J. Alloys Compd. 600, 29(2014) DOI URL
[37]	N. Anjabin, A. Karimi Taheri, H.S. Kim, Comput. Mater. Sci. 83, 78(2014) DOI URL
[38]	F. Jiang, H. Zhang, J. Mater. Sci. 53, 2830(2018) DOI URL
[39]	G. Bo, G. Wang, F. Jiang, C. Liu, R. Chen, H. Zhang, Rare Met. (2020). https://doi.org/10.1007/s1259 8-020-01382-9
[40]	G.H. Tao, C.H. Liu, J.H. Chen, Y.X. Lai, P.P. Ma, L.M. Liu, Mater. Sci. Eng. A 642, 241 (2015) DOI URL
[41]	Y.X. Lai, B.C. Jiang, C.H. Liu, Z.K. Chen, C.L. Wu, J.H. Chen, J. Alloys Compd. 701, 94(2017) DOI URL