Effect of Li addition on mechanical properties and ageing precipitation behavior of extruded Al−3.0Mg−0.5Si alloy

Abstract

The effect of Li (2.0 wt%) addition on mechanical properties and ageing precipitation behavior of Al−3.0Mg−0.5Si was investigated by tensile test, dynamic elasticity modulus test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images. The results show that the tensile strength of the Li-containing alloy can be significantly improved; however, the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture. The elasticity modulus of the Li-containing alloy increases by 11.6% compared with the base alloy. The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy, and δ′-Al₃Li phase becomes the main precipitates. Besides, β″-Mg₂Si and δ′-Al₃Li dual phases precipitation can be visibly observed at 170 °C ageing for 100 h, although the quantity of δ′-Al₃Li phase is more than β″-Mg₂Si phase. The width of the precipitate-free zone (PFZ) of the Li-containing alloy is much wider at the over-ageing state than the base alloy, which has a negative impact on the ductile and results in the decrease of elongation.

Keywords

Al−3.0Mg−0.5Si alloy / Li addition / microstructure / ageing behavior / mechanical properties / dynamic elasticity modulus

References

[1] DursunT, SoutisC. Recent developments in advanced aircraft aluminium alloys [J]. Materials & Design, 2014, 56: 862-871

[2] RiojaR J, LiuJ. The evolution of Al−Li base products for aerospace and space applications [J]. Metallurgical and Materials Transactions A, 2012, 43(9): 3325-3337

[3] GumbmannE, GeuserF D, SigliC, DeschampsA. Influence of Mg, Ag and Zn minor solute additions on the precipitation kinetics and strengthening of an Al−Cu−Li alloy [J]. Acta Materialia, 2017, 133: 172-185

[4] DengY-j, HuangG-j, CaoL-f, WuX-d, HuangL. Effect of ageing temperature on precipitation of Al−Cu−Li−Mn−Zr alloy [J]. Journal of Central South University, 2018, 25: 1340-1349

[5] LiJ-f, YeZ-h, LiuD-y, ChenY-l, ZhangX-h, XuX-z, ZhengZ-qiao. Influence of pre-deformation on aging precipitation behavior of three Al−Cu−Li alloys [J]. Acta Metallurgica Sinica (English Letters), 2017, 30(2): 133-145

[6] El-AtyA A, XuY, GuoX-z, ZhangS-h, MaY, ChenD-yonng. Strengthening mechanisms, deformation behavior, and anisotropic mechanical properties of Al-Li alloys: A review [J]. Journal of Advanced Research, 2018, 10: 49-67

[7] MaW-p, WangB-y, XiaoW-c, YangX-m, KangY. Springback analysis of 6016 aluminum alloy sheet in hot V-shape stamping [J]. Journal of Central South University, 2019, 26: 524-535

[8] ChbihiA, VincentS, RibisJ, Toffolon-MascletC, GarnierJ. Influence of plastic deformation on the precipitation sequence in an AA6061 alloy [J]. Journal of Materials Science, 2017, 52(10): 6063-6073

[9] KoshinoY, KozukaM, HirosawaS, YasuhiroA. Comparative and complementary characterization of precipitate microstructures in Al−Mg−Si(−Li) alloys by transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography [J]. Journal of Alloys and Compounds, 2015, 622: 765-770

[10] MørtsellE A, MarioaraC D, AndersenS J, RingdalenI G, FriisJ, WennerS, RøysetJ, ReisoO, HolmestadR. The effects and behaviour of Li and Cu alloying agents in lean Al−Mg−Si alloys [J]. Journal of Alloys and Compounds, 2017, 699: 235-242

[11] HuangZ W, SmallmanR E, LorettoM H, WhiteJ. Influence of lithium additions on precipitation and hardening of 6061 [J]. Materials Science and Technology, 1991, 7(3): 205-212

[12] HuangZ W, LorettoM H, SmallmanR E, WhiteJ. Mechanism of nucleation and precipitation in 6061-Li alloys [J]. Materials Science and Technology, 1994, 10: 869-878

[13] ChenR, HuangZ, ChenC Q, ShenJ Y, ZhangY G. Thermodynamic calculated and TEM observed microstructure of Al−Li−Mg−Si alloys [J]. Materials Science and Engineering A, 2000, 280(1): 146-150

[14] ShamasU D, KamranJ, TariqN H, HasanB A, PetrovR H, BliznukV, ShamasU Z. The synergistic effect of Li addition on microstructure, texture and mechanical properties of extruded Al−Mg−Si alloys [J]. Materials Chemistry and Physics, 2016, 174: 11-22

[15] YANG Xiao-kun, XIONG Bai-qing, LI Xi-wu, YAN Li-zhen, LI Zhi-hui, ZHANG Yong-an, LIU Hong-wei, HUANG Shu-hui, YAN Hong-wei, WEN Kai. Microstructural evolution and phase transformation of Al−Mg−Si alloy containing 3% Li during homogenization [C]// CMC 2018: Physics and Engineering of Metallic Materials. Springer, 2019: 19–28. DOI: https://doi.org/10.1007/978-981-13-5944-6_3.

[16] RiojaR J. Fabrication methods to manufacture isotropic Al−Li alloys and products for space and aerospace applications [J]. Materials Science and Engineering A, 1998, 257(1): 100-107

[17] LaverniaE J, SrivatsanT S, MohamedF A. Strength, deformation, fracture behaviour and ductility of aluminium-lithium alloys [J]. Journal of Materials Science, 1990, 25(2): 1137-1158

[18] WangS C, StarinkM J. Precipitates and intermetallic phases in precipitation hardening Al−Cu−Mg−(Li) based alloys [J]. International Materials Reviews, 2005, 50(4): 193-215

[19] DingL-p, JiaZ-h, NieJ-f, WengY-y, CaoL-f, ChenH-w, WuX-z, LiuQ. The structural and compositional evolution of precipitates in Al−Mg−Si−Cu alloy [J]. Acta Materialia, 2018, 145: 437-450

[20] JiaZ-h, DingL-p, CaoL-f, SandersR, LiS-c, LiuQ. The influence of composition on the clustering and precipitation behavior of Al−Mg−Si−Cu alloys [J]. Metallurgical Materials Transactions A, 2017, 48(1): 459-473

[21] WangY L, JiangH C, LiZ M, YanD S, ZhangD, RongL J. Two-stage double peaks ageing and its effect on stress corrosion cracking susceptibility of Al−Zn−Mg alloy [J]. Journal of Materials Science & Technology, 2018, 34(7): 1250-1257

[22] ZhangX-l, ZhangL, WuG-h, ShiC-c, ZhangJ-shuo. Influences of Mg content on the microstructures and mechanical properties of cast Al−2Li−2Cu−0.2Zr alloy [J]. Journal of Materials Science, 2019, 54(1): 791-811

[23] DengY-l, YangJ-l, LiS-y, ZhangJ, ZhangX-M. Influence of Li addition on mechanical property and aging precipitation behavior of Al−3.5Cu−1.5Mg alloy [J]. Transactions of Nonferrous Metals Society of China, 2014, 24(6): 1653-1658

[24] ChenX-x, MaX-w, XiH-k, ZhaoG-q, WangY-x, XuX. Effects of heat treatment on the microstructure and mechanical properties of extruded 2196 Al−Cu−Li alloy [J]. Materials & Design, 2020, 192108746

[25] ZhangJ, DengY-l, LiS-y, ChenZ-y, ZhangX-M. Creep age forming of 2124 aluminum alloy with single/double curvature [J]. Transactions of Nonferrous Metals Society of China, 2013, 23(7): 1922-1929

[26] ZhuA W, StarkeE A. Strengthening effect of unshearable particles of finite site: A compu-ter experimental study [J]. Acta Materialia, 1999, 47(11): 3263-3269