Effect of Natural Aging on Artificial Aging of an Al-2.95Cu-1.55Li-0.57Mg-0.18Zr Alloy at 160oC

doi:10.11900/0412.1961.2021.00405

Acta Metall Sin

2023, Vol. 59

Issue (11): 1428-1438 DOI: 10.11900/0412.1961.2021.00405

Current Issue | Archive | Adv Search

Effect of Natural Aging on Artificial Aging of an Al-2.95Cu-1.55Li-0.57Mg-0.18Zr Alloy at 160^oC

GONG Xiangpeng, WU Cuilan(

), LUO Shifang, SHEN Ruohan, YAN Jun

Center for High-Resolution Electron Microscopy, College of Materials Science and Engineering, Hunan University, Changsha 410012, China

Cite this article:

GONG Xiangpeng, WU Cuilan, LUO Shifang, SHEN Ruohan, YAN Jun. Effect of Natural Aging on Artificial Aging of an Al-2.95Cu-1.55Li-0.57Mg-0.18Zr Alloy at 160^oC. Acta Metall Sin, 2023, 59(11): 1428-1438.

Download:

HTML

PDF(4508KB)
Export: BibTeX | EndNote (RIS)

Abstract

Due to their excellent combination of low density, high strength, and stiffness, third-generation Al-Cu-Li-Mg alloys are important lightweight materials in the aerospace industry. Precipitation strengthening or hardening, which is controlled by precipitates, including the structure, size, morphology, distribution, and volume fraction of precipitates, is mainly responsible for the alloy's excellent mechanical properties. The precipitates in Al-Cu-Li-Mg alloys mainly include T₁, S, δ', δ'/θ'/δ', θ', GPB, and various metastable phases. In practice, the Al alloys are inevitably stored for a period at ambient temperature before subsequent processing during which natural aging occurs. Natural aging has an important effect on the precipitation behavior of subsequent artificial aging in Al-Cu-Li-Mg alloys, but the related mechanism is still highly controversial. To solve this problem, the effects of natural aging treatment on the microstructure and mechanical properties of an Al-2.95Cu-1.55Li-0.57Mg-0.18Zr alloy treated by artificial aging at 160^oC were investigated using TEM, three-dimensional atom probe (3DAP), three-dimensional electron tomography (3DET), and mechanical property testing. It was discovered that natural aging significantly changed the artificial aging hardening behavior and caused two strengthening peaks in the alloy's hardness curve. The Mg-rich and Cu-Mg clusters and δ' precipitates formed during natural aging were first dissolved at the initial stage of artificial aging, which resulted in a decrease in hardness. Then, large numbers of GPB zones formed uniformly and dispersedly, followed by the formation of T₁ precipitates with the increase of aging time, which caused the increase in hardness. The hardness reached its first peak value at 96 h. Following that, GPB zones dissolved and the hardness decreased again. When the aging time was continuously exceeded, the volume fraction of T₁ precipitates and the number of lath-like S precipitates increased, so the hardness increased again and reached the second peak value at 192 h. In other words, the atomic clusters that form during natural aging can significantly modify precipitation behaviors and the evolution of mechanical properties during artificial aging.

Key words: Al-Cu-Li-Mg alloy natural aging aging precipitation behavior atomic cluster

Received: 17 September 2021

ZTFLH:

TG156

Fund: National Natural Science Foundation of China(51831004);National Natural Science Foundation of China(52171006);National Natural Science Foundation of China(11427806)

Corresponding Authors: WU Cuilan, professor, Tel: (0731)88664010, E-mail: cuilanwu@hnu.edu.cn

	Service

	E-mail this article
	Add to citation manager
	E-mail Alert
	RSS
	（）
	Articles by authors
	GONG Xiangpeng
	WU Cuilan
	LUO Shifang
	SHEN Ruohan
	YAN Jun

URL:

https://www.ams.org.cn/EN/10.11900/0412.1961.2021.00405 OR https://www.ams.org.cn/EN/Y2023/V59/I11/1428

Fig.1 Mechanical properties of the alloys with T6 and T66 treatment
(a) age-hardening curves vs aging time
(b) engineering stress-strain curves of peak-aged T6 alloys at 96 and 192 h, respectively
(c) engineering stress-strain curves of peak-aged T66 alloys at 96 and 192 h, respectively
(d) diagram of tensile properties

Fig.2 Microstructures and T₁ diameter distribution of the peak-aged T6 sample for 96 h
(a) HAADF image of precipitates viewed along the [001]_Al direction
(b) atomic-resolution HAADF images of rod-like S precipitates and GPB zones viewed along the [001]_Al direction
(c) HAADF image of T₁ precipitates viewed along the [110]_Aldirection (Inset is the atomic-resolution image of a T₁ precipitate)
(d) T₁ diameter distribution

Fig.3 Microstructures and T₁ diameter distribution of the peak-aged T6 sample at 192 h
(a) HAADF image of precipitates viewed along the [001]_Al direction (Inset is the corresponding atomic-resolution HAADF image of a δ'/θ'/δ' composite precipitate)
(b) HAADF image of T₁ precipitates viewed along the [110]_Al direction
(c) T₁ diameter distribution

Fig.4 TEM images of microstructures of the sample which is natural aged (NA) for 7 d
(a) atomic-resolution HAADF image of δ'-phase precipitates viewed along the [001]_Al orientation (Inset is the selected area electron diffraction (SAED) pattern)
(b) atomic-resolution HAADF image of GPI zones viewed along the [001]_Al orientation

Fig.5 3DAP analyses of atomic clusters in the sample which is natural aged for 7 d (d_pair—distance between nearest-neighbor atoms)
(a) nearest-neighbor analysis of Mg (b) nearest-neighbor analysis of Cu
(c) distribution of Mg clusters and Mg-Cu co-clusters

Fig.6 HAADF-STEM images and SAED pattern of the T66 sample aged for 8 h
(a) morphology of precipitates viewed along [001]_Al direction and SAED pattern (inset)
(b) morphology of T₁ precipitates viewed along [110]_Al direction

Fig.7 HAADF-STEM images of the first-peak-aged T66 sample at 96 h
(a) morphology of precipitates viewed along the [001]_Al direction
(b) atomic-resolution HAADF images of the precipitates viewed along the [001]_Al direction
(c) morphology of T₁ precipitates viewed along the [110]_Al direction (Inset is the atomic-resolution HAADF image of a T₁ precipitate)

Fig.8 HAADF-STEM images of the valley-aged T66 sample at 144 h
(a) morphology of precipitates viewed along the [001]_Al direction (Insets are the corresponding atomic-resolution HAADF images of the precipitates)
(b) morphology of T₁ precipitates viewed along the [110]_Aldirection (Inset is the atomic-resolution HAADF image of a T₁ precipitate)

Fig.9 HAADF-STEM images of the second-peak-aged T66 sample at 192 h
(a) morphology of precipitates viewed along the [001]_Al direction (Inset is the atomic-resolution HAADF image of a lath-like S precipitate)
(b) morphology of T₁ precipitates viewed along [110]_Al direction (Inset is the atomic-resolution HAADF image of a T₁ precipitate)

Fig.10 Statistics of T₁ precipitate diameter of samples with T66 treatment
(a) first-peak-aged sample (b) valley-aged sample
(c) second-peak-aged sample (d) aspect ratios of T₁ phases

Fig.11 3DET images of precipitates in the two peak-aged T66 samples and the number density of T₁ precipitates
(a, b) plain view of peak 1 (a) and peak 2 (b), respectively
(c, d) top-down view of peak 1 (c) and peak 2 (d), respectively
(e) number density of T₁ precipitates

Fig.12 Schematic of mechanical properties and microstructure evolution of the T66 alloy

1	Rioja R J, Liu J. The evolution of Al-Li base products for aerospace and space applications [J]. Metall. Mater. Trans., 2012, 43A: 3325
2	Rioja R J. Fabrication methods to manufacture isotropic Al-Li alloys and products for space and aerospace applications [J]. Mater. Sci. Eng., 1998, A257: 100
3	Gao Z, Chen J H, Duan S Y, et al. Complex precipitation sequences of Al-Cu-Li-(Mg) alloys characterized in relation to thermal ageing processes [J]. Acta Metal. Sin. (Engl. Lett.), 2016, 29: 94 doi: 10.1007/s40195-016-0366-5
4	Dorin T, Deschamps A, De Geuser F, et al. Quantification and modelling of the microstructure/strength relationship by tailoring the morphological parameters of the T₁ phase in an Al-Cu-Li alloy [J]. Acta Mater., 2014, 75: 134 doi: 10.1016/j.actamat.2014.04.046
5	Gable B M, Zhu A W, Csontos A A, et al. The role of plastic deformation on the competitive microstructural evolution and mechanical properties of a novel Al-Li-Cu-X alloy [J]. J. Light Met., 2001, 1: 1 doi: 10.1016/S1471-5317(00)00002-X
6	Rodgers B I, Prangnell P B. Quantification of the influence of increased pre-stretching on microstructure-strength relationships in the Al-Cu-Li alloy AA2195 [J]. Acta Mater., 2016, 108: 55 doi: 10.1016/j.actamat.2016.02.017
7	Van Smaalen S, Meetsma A, De Boer J L, et al. Refinement of the crystal structure of hexagonal Al₂CuLi [J]. J. Solid State Chem., 1990, 85: 293 doi: 10.1016/S0022-4596(05)80086-6
8	Tsivoulas D, Robson J D. Heterogeneous Zr solute segregation and Al₃Zr dispersoid distributions in Al-Cu-Li alloys [J]. Acta Mater., 2015, 93: 73 doi: 10.1016/j.actamat.2015.03.057
9	Gao Z, Liu J Z, Chen J H, et al. Formation mechanism of precipitate T₁ in AlCuLi alloys [J]. J. Alloys Compd., 2015, 624: 22 doi: 10.1016/j.jallcom.2014.10.208
10	Liu Z R, Chen J H, Wang S B, et al. The structure and the properties of S-phase in AlCuMg alloys [J]. Acta Mater., 2011, 59: 7396 doi: 10.1016/j.actamat.2011.08.009
11	Styles M J, Hutchinson C R, Chen Y, et al. The coexistence of two S (Al₂CuMg) phases in Al-Cu-Mg alloys [J]. Acta Mater., 2012, 60: 6940 doi: 10.1016/j.actamat.2012.08.044
12	Yoshimura R, Konno T J, Abe E, et al. Transmission electron microscopy study of the early stage of precipitates in aged Al-Li-Cu alloys [J]. Acta Mater., 2003, 51: 2891 doi: 10.1016/S1359-6454(03)00104-6
13	Konno T J, Hiraga K, Kawasaki M. Guinier-Preston (GP) zone revisited: Atomic level observation by HAADF-TEM technique [J]. Scr. Mater., 2001, 44: 2303 doi: 10.1016/S1359-6462(01)00909-5
14	Duan S Y, Wu C L, Gao Z, et al. Interfacial structure evolution of the growing composite precipitates in Al-Cu-Li alloys [J]. Acta Mater., 2017, 129: 352 doi: 10.1016/j.actamat.2017.03.018
15	Ringer S P, Sakurai T, Polmear I J. Origins of hardening in aged Al-Cu-Mg-(Ag) alloys [J]. Acta Mater., 1997, 45: 3731 doi: 10.1016/S1359-6454(97)00039-6
16	Reich L, Ringer S P, Hono K. Origin of the initial rapid age hardening in an Al-1.7at.%Mg-1.1at.%Cu alloy [J]. Philos. Mag. Lett., 1999, 79: 639 doi: 10.1080/095008399176689
17	Kovarik L, Court S A, Fraser H L, et al. GPB zones and composite GPB/GPBII zones in Al-Cu-Mg alloys [J]. Acta Mater., 2008, 56: 4804 doi: 10.1016/j.actamat.2008.05.042
18	Kovarik L, Mills M J. Structural relationship between one-dimensional crystals of Guinier-Preston-Bagaryatsky zones in Al-Cu-Mg alloys [J]. Scr. Mater., 2011, 64: 999 doi: 10.1016/j.scriptamat.2011.01.033
19	Kovarik L, Mills M J. Ab initio analysis of Guinier-Preston-Bagaryatsky zone nucleation in Al-Cu-Mg alloys [J]. Acta Mater., 2012, 60: 3861 doi: 10.1016/j.actamat.2012.03.044
20	Duan S Y, Le Z, Chen Z K, et al. Li-atoms-induced structure changes of Guinier-Preston-Bagaryatsky zones in AlCuLiMg alloys [J]. Mater. Charact., 2016, 121: 207 doi: 10.1016/j.matchar.2016.09.037
21	Gong X P, Luo S F, Li S Y, et al. Dislocation-induced precipitation and its strengthening of Al-Cu-Li-Mg alloys with high Mg [J]. Acta Metal. Sin. (Engl. Lett.), 2021, 34: 597 doi: 10.1007/s40195-020-01166-1
22	Decreus B, Deschamps A, De Geuser F, et al. The influence of Cu/Li ratio on precipitation in Al-Cu-Li-x alloys [J]. Acta Mater., 2013, 61: 2207 doi: 10.1016/j.actamat.2012.12.041
23	Ma P P, Zhan L H, Liu C H, et al. Pre-strain-dependent natural ageing and its effect on subsequent artificial ageing of an Al-Cu-Li alloy [J]. J. Alloys Compd., 2019, 790: 8 doi: 10.1016/j.jallcom.2019.03.072
24	Li S Y, Wang Q, Chen J H, et al. The effect of thermo-mechanical treatment on the formation of T₁ phase and δ'/θ'/δ' composite precipitate in an Al-Cu-Li-Mg alloy [J]. Mater. Charact., 2021, 176: 111123 doi: 10.1016/j.matchar.2021.111123
25	Liu C H, Lai Y X, Chen J H, et al. Natural-aging-induced reversal of the precipitation pathways in an Al-Mg-Si alloy [J]. Scr. Mater., 2016, 115: 150 doi: 10.1016/j.scriptamat.2015.12.027
26	Pogatscher S, Antrekowitsch H, Leitner H, et al. Mechanisms controlling the artificial aging of Al-Mg-Si Alloys [J]. Acta Mater., 2011, 59: 3352 doi: 10.1016/j.actamat.2011.02.010
27	Martinsen F A, Ehlers F J H, Torsæter M, et al. Reversal of the negative natural aging effect in Al-Mg-Si alloys [J]. Acta Mater., 2012, 60: 6091 doi: 10.1016/j.actamat.2012.07.047
28	Deschamps A, Garcia M, Chevy J, et al. Influence of Mg and Li content on the microstructure evolution of Al-Cu-Li alloys during long-term ageing [J]. Acta Mater., 2017, 122: 32 doi: 10.1016/j.actamat.2016.09.036
29	Wu L, Chen Y C, Li X F, et al. Rapid hardening during natural aging of Al-Cu-Li based alloys with Mg addition [J]. Mater. Sci. Eng., 2019, A743: 741
30	Ivanov R, Deschamps A, De Geuser F. Clustering kinetics during natural ageing of Al-Cu based alloys with (Mg, Li) additions [J]. Acta Mater., 2018, 157: 186 doi: 10.1016/j.actamat.2018.07.035
31	Nellist P D, Pennycook S J. Incoherent imaging using dynamically scattered coherent electrons [J]. Ultramicroscopy, 1999, 78: 111 doi: 10.1016/S0304-3991(99)00017-0
32	Hillyard S, Silcox J. Detector geometry, thermal diffuse scattering and strain effects in ADF STEM imaging [J]. Ultramicroscopy, 1995, 58: 6 doi: 10.1016/0304-3991(94)00173-K
33	Wang Z M, Li H, Shen Q, et al. Nano-precipitates evolution and their effects on mechanical properties of 17-4 precipitation-hardening stainless steel [J]. Acta Mater., 2018, 156: 158 doi: 10.1016/j.actamat.2018.06.031
34	Duan S Y. The influence of lithium on the ageing precipitation behavior of Al-Cu-Mg alloys [D]. Changsha: Hunan University, 2017
	段石云. 合金元素锂对Al-Cu-Mg合金时效析出行为的影响 [D]. 长沙: 湖南大学, 2017
35	Zhu A W, Gable B M, Shiflet G J, et al. Trace element effects on precipitation in Al-Cu-Mg-(Ag, Si) alloys: A computational analysis [J]. Acta Mater., 2004, 52: 3671 doi: 10.1016/j.actamat.2004.04.021
36	Zhu A W, Starke Jr E A, Shiflet G J. An FP-CVM calculation of pre-precipitation clustering in Al-Cu-Mg-Ag alloys [J]. Scr. Mater., 2005, 53: 35 doi: 10.1016/j.scriptamat.2005.03.023
37	Starink M J, Wang S C. The thermodynamics of and strengthening due to co-clusters: General theory and application to the case of Al-Cu-Mg alloys [J]. Acta Mater., 2009, 57: 2376 doi: 10.1016/j.actamat.2009.01.021
38	Ringer S P, Hono K, Sakurai T, et al. Cluster hardening in an aged Al-Cu-Mg alloy [J]. Scr. Mater., 1997, 36: 517 doi: 10.1016/S1359-6462(96)00415-0

[1]	ZHU Shize, WANG Dong, WANG Quanzhao, XIAO Bolv, MA Zongyi. Influence of Cu Content on the Negative Effect of Natural Aging in SiC/Al-Mg-Si-Cu Composites[J]. 金属学报, 2021, 57(7): 928-936.
[2]	Zhao Yi. Molecular dynamics simulation of the nucleation in a supercooled liquid Ni3Al[J]. 金属学报, 2008, 44(10): 1157-1160 .
[3]	XIA Junhai; QIANG Jianbing; WANG Yingmin; WANG Qing; HUANG Huogen; DONG Chuang. FORMATION OF Cu-BASED BULK AMORPHOUS ALLOY IN THE Cu-Zr-Nb SYSTEM[J]. 金属学报, 2005, 41(9): 999-1003 .

No Suggested Reading articles found!

Viewed

Full text

Abstract

Cited

Shared

Discussed