Effects of Zn Addition on the Natural Ageing Behavior and Bake Hardening Response of a Pre-Aged Al-Mg-Si-Cu Alloy

doi:10.11900/0412.1961.2018.00555

Acta Metall Sin

2019, Vol. 55

Issue (11): 1395-1406 DOI: 10.11900/0412.1961.2018.00555

Current Issue | Archive | Adv Search

Effects of Zn Addition on the Natural Ageing Behavior and Bake Hardening Response of a Pre-Aged Al-Mg-Si-Cu Alloy

ZHU Shang¹,LI Zhihui¹(

),YAN Lizhen¹,LI Xiwu¹,ZHANG Yongan¹,XIONG Baiqing^1,²

1. State Key Laboratory of Nonferrous Metals and Processes, GRINMAT Engineering Institute Co. , Ltd. , Beijing 101407, China
2. GRINM Group Co. , Ltd. , Beijing 100088, China

Cite this article:

ZHU Shang,LI Zhihui,YAN Lizhen,LI Xiwu,ZHANG Yongan,XIONG Baiqing. Effects of Zn Addition on the Natural Ageing Behavior and Bake Hardening Response of a Pre-Aged Al-Mg-Si-Cu Alloy. Acta Metall Sin, 2019, 55(11): 1395-1406.

Download:

HTML

PDF(10423KB)
Export: BibTeX | EndNote (RIS)

Abstract

Al-Mg-Si(-Cu) alloys are widely used in automotive body panels because of their excellent combined performance of high strength-to-weight ratio, good formability and corrosion resistance. Zn additions to Al-Mg-Si(-Cu) alloys have been tested and shown to effectively affect the precipitation microstructure and enhance the age-hardening response. The present study investigates the natural ageing (NA) behavior and bake hardening response in the pre-aged Al-0.9Mg-0.8Si-0.2Cu (mass fraction, %) and Al-0.9Mg-0.8Si-0.2Cu-0.6Zn (mass fraction, %) alloys. The results are compared to clarify the effect of Zn addition. During NA after pre-ageing at 80 ℃ for 15 min (PA), cluster growth is the dominant process in the Zn-free and Zn-added alloys. Some Zn atoms are partitioned into the clusters under PA+NA condition. Partitioning of Zn may change the stability of clusters, increasing the growth rate of clusters. The yield strength of the two alloys increases with the increasing NA time. The smaller cluster spacing and larger cluster shear modulus lead to the higher yield strength in the Zn-added alloy during NA after PA. The prolonged NA inhibits the transformation of clusters to GP zones and β″ phases during bake hardening (BH) treatment at 170 ℃ for 30 min in the Zn-free and Zn-added alloys, resulting in the lower BH response. The Zn does not significantly partition into clusters or precipitates, and the majority of Zn remains in the Al matrix during BH treatment, prompting the transformation from solute clusters to GP zones and β″ phases. As a result, the yield strength of the Zn-added alloy after PA+NA+BH treatment is higher than that of the Zn-free alloy.

Key words: Al-Mg-Si-Cu alloy ageing Zn addition precipitate

Received: 19 December 2018

ZTFLH:

TG146.21

Fund: National Key Research and Development Program of China(2016YFB0300802)

	Service

	E-mail this article
	Add to citation manager
	E-mail Alert
	RSS
	（）
	Articles by authors
	Shang ZHU
	Zhihui LI
	Lizhen YAN
	Xiwu LI
	Yongan ZHANG
	Baiqing XIONG

URL:

https://www.ams.org.cn/EN/10.11900/0412.1961.2018.00555 OR https://www.ams.org.cn/EN/Y2019/V55/I11/1395

Table 1 Chemical compositions of the Zn-free and Zn-added Al-Mg-Si-Cu alloys (mass fraction / %)

Fig.1 Schematic of heat treatment process

Fig.2 Vickers hardness curves of the pre-aged Zn-free and Zn-added alloys during natural ageing (a) and subsequent bake-hardening treatment (b)

Table 2 Tensile properties of the pre-aged Zn-free and Zn-added alloys during natural ageing and subsequent bake-hardening treatment

Fig.3 Morphologies of precipitates observed by 3DAP in the Zn-free and Zn-added alloys during natural ageing after pre-ageingColor online(a) Zn-free alloy after PA+NA 2 d (The analyzed volume is 133 nm×75 nm ×77 nm)(b) Zn-added alloy after PA+NA 2 d (The analyzed volume is 160 nm×57 nm ×59 nm)(c) Zn-free alloy after PA+NA 120 d (The analyzed volume is 260 nm×40 nm ×41 nm)(d) Zn-added alloy after PA+NA 120 d (The analyzed volume is 279 nm×54 nm×55 nm)

Fig.4 Morphologies of precipitates observed by 3DAP in the pre-aged Zn-free and Zn-added alloys under different ageing conditionsColor online(a) Zn-free alloy after PA+NA 2 d+BH (The analyzed volume is 181 nm×103 nm×105 nm)(b) Zn-added alloy after PA+NA 2 d+BH (The analyzed volume is 286 nm×79 nm×81 nm)(c) Zn-free alloy after PA+NA 120 d+BH (The analyzed volume is 331 nm×79 nm×82 nm)(d) Zn-added alloy after PA+NA 120 d+BH (The analyzed volume is 328 nm×77 nm×77 nm)

Fig.5 Relationships between the size and shape of precipitates in the Zn-free (a, c, e, g) and Zn-added (b, d, f, h) alloys under different ageing conditions (x, y and z are the dimensions of each precipitate measured along three orthogonal axes of best-fit ellipsoid)(a, b) PA+NA 2 d (c, d) PA+NA 120 d(e, f) PA+NA 2 d+BH (g, h) PA+NA 120 d+BH

Fig.6 Number densities of precipitates in the pre-aged Zn-free (a) and Zn-added (b) alloys during natural ageing and subsequent bake-hardening treatment

Fig.7 Fractions of the total amounts of solute atoms incorporated in the precipitates of pre-aged Zn-free and Zn-added alloys under different ageing conditions (For example, 4.56% of the total amount of Mg in the Zn-free alloy after PA+NA 2 d was incorporated in clusters, so 95.44% of the Mg remained in the matrix. Different types of precipitates are distinguished in Fig.5)(a) Zn-free alloy after PA+NA 2 d and PA+NA 2 d+BH(b) Zn-free alloy after PA+NA 120 d and PA+NA 120 d+BH(c) Zn-added alloy after PA+NA 2 d and PA+NA 2 d+BH(d) Zn-added alloy after PA+NA 120 d and PA+NA 120 d+BH

Table 3 Calculated yield strengths of the pre-aged Zn-free and Zn-added alloys during NA after PA (Clusters are identified in Figs.5a~d)

Table 4 Calculated yield strengths of the pre-aged Zn-free and Zn-added alloys during BH treatment after NA (Different types of precipitates are distinguished in Figs.5e~h)

Table 5 Changes in the average radius and the Mg/Si ratio of clusters in the Zn-free and Zn-added alloys and the Mg/Zn ratio of clusters in the Zn-added alloy during NA after PA

Fig.8 Schematics of precipitation evolution in the pre-aged Zn-free (a) and Zn-added (b) alloys during NA and BH treatmentsColor online

[1]	PogatscherS, AntrekowitschH, LeitnerH, et al. Mechanisms controlling the artificial aging of Al-Mg-Si alloys [J]. Acta Mater., 2011, 59: 3352
[2]	EdwardsG A, StillerK, DunlopG L, et al. The precipitation sequence in Al-Mg-Si alloys [J]. Acta Mater., 1998, 46: 3893
[3]	WengY Y, JiaZ H, DingL P, et al. Clustering behavior during natural aging and artificial aging in Al-Mg-Si alloys with different Ag and Cu addition [J]. Mater. Sci. Eng., 2018, A732: 273
[4]	MartinsenF A, EhlersF J H, Tors?terM, et al. Reversal of the negative natural aging effect in Al-Mg-Si alloys [J]. Acta Mater., 2012, 60: 6091
[5]	FallahV, KorinekA, Ofori-OpokuN, et al. Atomic-scale pathway of early-stage precipitation in Al-Mg-Si alloys [J]. Acta Mater., 2015, 82: 457
[6]	MurayamaM, HonoK, MiaoW F, et al. The effect of Cu additions on the precipitation kinetics in an Al-Mg-Si alloy with excess Si [J]. Metall. Mater. Trans., 2001, 32A: 239
[7]	NiniveP H, StrandlieA, Gulbrandsen-DahlS, et al. Detailed atomistic insight into the β″ phase in Al-Mg-Si alloys [J]. Acta Mater., 2014, 69: 126
[8]	YangW C, WangM P, ZhangR R, et al. The diffraction patterns from β″ precipitates in 12 orientations in Al-Mg-Si alloy [J]. Scr. Mater., 2010, 62: 705
[9]	DingL P, HeY, WenZ, et al. Optimization of the pre-aging treatment for an AA6022 alloy at various temperatures and holding times [J]. J. Alloys Compd., 2015, 647: 238
[10]	SerizawaA, HirosawaS, SatoT. Three-dimensional atom probe characterization of nanoclusters responsible for multistep aging behavior of an Al-Mg-Si alloy [J]. Metall. Mater. Trans., 2008, 39A: 243
[11]	ArugaY, KozukaM, TakakiY, et al. Evaluation of solute clusters associated with bake-hardening response in isothermal aged Al-Mg-Si alloys using a three-dimensional atom probe [J]. Metall. Mater. Trans., 2014, 45A: 5906
[12]	Tors?terM, HastingH S, LefebvreW, et al. The influence of composition and natural aging on clustering during preaging in Al-Mg-Si alloys [J]. J. Appl. Phys., 2010, 108: 0735527
[13]	ZandbergenM W, XuQ, CerezoA, et al. Study of precipitation in Al-Mg-Si alloys by atom probe tomography I. Microstructural changes as a function of ageing temperature [J]. Acta Mater., 2015, 101: 136
[14]	TakakiY, MasudaT, KobayashiE, et al. Effects of natural aging on bake hardening behavior of Al-Mg-Si alloys with multi-step aging process [J]. Mater. Trans., 2014, 55: 1257
[15]	ArugaY, KozukaM, TakakiY, et al. Effects of natural aging after pre-aging on clustering and bake-hardening behavior in an Al-Mg-Si alloy [J]. Scr. Mater., 2016, 116: 82
[16]	DingX P, CuiH, ZhangJ X, et al. The effect of Zn on the age hardening response in an Al-Mg-Si alloy [J]. Mater. Des., 2015, 65: 1229
[17]	YanL Z, ZhangY A, LiX W, et al. Effect of Zn addition on microstructure and mechanical properties of an Al-Mg-Si alloy [J]. Prog. Nat. Sci.Mater. Int., 2014, 24: 97
[18]	SaitoT, WennerS, OsmundsenE, et al. The effect of Zn on precipitation in Al-Mg-Si alloys [J]. Philos. Mag., 2014, 94: 2410
[19]	GuoM X, ZhangY, ZhangX K, et al. Non-isothermal precipitation behaviors of Al-Mg-Si-Cu alloys with different Zn contents [J]. Mater. Sci. Eng., 2016, A669: 20
[20]	HonoK. Atom probe microanalysis and nanoscale microstructures in metallic materials [J]. Acta Mater., 1999, 47: 3127
[21]	WangB, WangX J, SongH, et al. Strengthening effects of microstructure evolution during early ageing process in Al-Mg-Si alloy [J]. Acta Metall. Sin., 2014, 50: 685
[21]	汪波, 王晓姣, 宋辉等. Al-Mg-Si合金时效早期显微组织演变及其对强化的影响 [J]. 金属学报, 2014, 50: 685
[22]	ShaG, M?llerH, StumpfW E, et al. Solute nanostructures and their strengthening effects in Al-7Si-0.6Mg alloy F357 [J]. Acta Mater., 2012, 60: 692
[23]	BuhaJ, LumleyR N, CroskyA G, et al. Secondary precipitation in an Al-Mg-Si-Cu alloy [J]. Acta Mater., 2007, 55: 3015
[24]	LiH, LiuW Q. Nanoprecipitates and their strengthening behavior in Al-Mg-Si alloy during the aging process [J]. Metall. Mater. Trans., 2017, 48A: 1990
[25]	KarneskyR A, SudbrackC K, SeidmanD N. Best-fit ellipsoids of atom-probe tomographic data to study coalescence of γ′ (L12) precipitates in Ni-Al-Cr [J]. Scr. Mater., 2007, 57: 353
[26]	GaultB, MoodyM P, CairneyJ M, et al. Atom Probe Microscopy [M]. New York: Springer, 2012: 270
[27]	EsmaeiliS, LloydD J, PooleW J. Modeling of precipitation hardening for the naturally aged Al-Mg-Si-Cu alloy AA6111 [J]. Acta Mater., 2003, 51: 3467
[28]	StarinkM J, CaoL F, RometschP A. A model for the thermodynamics of and strengthening due to co-clusters in Al-Mg-Si-based alloys [J]. Acta Mater., 2012, 60: 4194
[29]	MarceauR K W, de VaucorbeilA, ShaG, et al. Analysis of strengthening in AA6111 during the early stages of aging: Atom probe tomography and yield stress modelling [J]. Acta Mater., 2013, 61: 7285
[30]	BrandesE A, BrookG B. Smithells Metals Reference Book [M]. 7th Ed., London: Butterworth-Heinemann, 1992: 15
[31]	LiuG, ZhangG J, DingX D, et al. Modeling the strengthening response to aging process of heat-treatable aluminum alloys containing plate/disc- or rod/needle-shaped precipitates [J]. Mater. Sci. Eng., 2003, A344: 113
[32]	SeidmanD N, MarquisE A, DunandD C. Precipitation strengthening at ambient and elevated temperatures of heat-treatable Al(Sc) alloys [J]. Acta Mater., 2002, 50: 4021
[33]	KingH W. Quantitative size-factors for metallic solid solutions [J]. J. Mater. Sci., 1966, 1: 79
[34]	ZandbergenM W, CerezoA, SmithG D W. Study of precipitation in Al-Mg-Si alloys by atom probe tomography II. Influence of Cu additions [J]. Acta Mater., 2015, 101: 149
[35]	ArugaY, KozukaM, TakakiY, et al. Formation and reversion of clusters during natural aging and subsequent artificial aging in an Al-Mg-Si alloy [J]. Mater. Sci. Eng., 2015, A631: 86
[36]	AdachiH, NakanishiH, AsanoM. Soft X-ray XAFS studies on Al-Mg-Si alloys with different aging conditions [J]. J. Jpn.Inst.Light Met., 2015, 65: 411(足立大樹, 中西英貴, 浅野峰生. 時効条件が異なるAl-Mg-Si合金における軟X線XAFS測定 [J]. 軽金属, 2015, 65: 411
[37]	ZhuS, LiZ H, YanL Z, et al. Effects of Zn addition on the age hardening behavior and precipitation evolution of an Al-Mg-Si-Cu alloy [J]. Mater. Charact., 2018, 145: 258

[1]	LU Yuhua, WANG Haizhou, LI Dongling, FU Rui, LI Fulin, SHI Hui. A Quantitative and Statistical Method of γ' Precipitates in Superalloy Based on the High-Throughput Field Emission Scanning Eelectron Microscope[J]. 金属学报, 2023, 59(7): 841-854.
[2]	LIU Manping, XUE Zhoulei, PENG Zhen, CHEN Yulin, DING Lipeng, JIA Zhihong. Effect of Post-Aging on Microstructure and Mechanical Properties of an Ultrafine-Grained 6061 Aluminum Alloy[J]. 金属学报, 2023, 59(5): 657-667.
[3]	CHEN Kaixuan, LI Zongxuan, WANG Zidong, Demange Gilles, CHEN Xiaohua, ZHANG Jiawei, WU Xuehua, Zapolsky Helena. Morphological Evolution of Fe-Rich Precipitates in a Cu-2.0Fe Alloy During Isothermal Treatment[J]. 金属学报, 2023, 59(12): 1665-1674.
[4]	MA Guonan, ZHU Shize, WANG Dong, XIAO Bolv, MA Zongyi. Aging Behaviors and Mechanical Properties of SiC/Al-Zn-Mg-Cu Composites[J]. 金属学报, 2023, 59(12): 1655-1664.
[5]	RUI Xiang, LI Yanfen, ZHANG Jiarong, WANG Qitao, YAN Wei, SHAN Yiyin. Microstructure and Mechanical Properties of a Novel Designed 9Cr-ODS Steel Synergically Strengthened by Nano Precipitates[J]. 金属学报, 2023, 59(12): 1590-1602.
[6]	LI Xiaolin, LIU Linxi, LI Yating, YANG Jiawei, DENG Xiangtao, WANG Haifeng. Mechanical Properties and Creep Behavior of MX-Type Precipitates Strengthened Heat Resistant Martensite Steel[J]. 金属学报, 2022, 58(9): 1199-1207.
[7]	LIU Xuxi, LIU Wenbo, LI Boyan, HE Xinfu, YANG Zhaoxi, YUN Di. Calculation of Critical Nucleus Size and Minimum Energy Path of Cu-Riched Precipitates During Radiation in Fe-Cu Alloy Using String Method[J]. 金属学报, 2022, 58(7): 943-955.
[8]	WANG Shuo, WANG Junsheng. Structural Evolution and Stability of the δ′/θ′/δ′ Composite Precipitate in Al-Li Alloys: A First-Principles Study[J]. 金属学报, 2022, 58(10): 1325-1333.
[9]	WANG Xue, LI Yong, WANG Jiaqing, HU Lei. Effect of High Temperature Ageing on Microstructure and Stress-Relief Cracking Susceptibility of Coarse Grain Heat Affected Zone in T23 steel[J]. 金属学报, 2021, 57(6): 736-748.
[10]	YE Junjie, HE Zhirong, ZHANG Kungang, DU Yuqing. Effect of Ageing on Microsturcture, Tensile Properties, and Shape Memory Behaviors of Ti-50.8Ni-0.1Zr Shape Memory Alloy[J]. 金属学报, 2021, 57(6): 717-724.
[11]	GAO Yihan, LIU Gang, SUN Jun. Recent Progress in High-Temperature Resistant Aluminum-Based Alloys: Microstructural Design and Precipitation Strategy[J]. 金属学报, 2021, 57(2): 129-149.
[12]	LIU Chao, YAO Zhihao, GUO Jing, PENG Zichao, JIANG He, DONG Jianxin. Microstructure Evolution Behavior of Powder Superalloy FGH4720Li at Near Service Temperature[J]. 金属学报, 2021, 57(12): 1549-1558.
[13]	GUO Qianying, LI Yanmo, CHEN Bin, DING Ran, YU Liming, LIU Yongchang. Effect of High-Temperature Ageing on Microstructure and Creep Properties of S31042 Heat-Resistant Steel[J]. 金属学报, 2021, 57(1): 82-94.
[14]	LIU Feng, WANG Tianle. Precipitation Modeling via the Synergy of Thermodynamics and Kinetics[J]. 金属学报, 2021, 57(1): 55-70.
[15]	LI Jichen, FENG Di, XIA Weisheng, LIN Gaoyong, ZHANG Xinming, REN Minwen. Effect of Non-Isothermal Ageing on Microstructure and Properties of 7B50 Aluminum Alloy[J]. 金属学报, 2020, 56(9): 1255-1264.

No Suggested Reading articles found!

Viewed

Full text

Abstract

Cited

Shared

Discussed