Effects of Cu addition on microstructure and mechanical properties of Er-modified Al-10Mg₂Si cast alloys

Abstract

The solidification microstructure and mechanical properties of hypoeutectic Al-10Mg₂Si cast alloys with different Cu contents and 0.45 wt.% Er were investigated using an optical microscope, scanning electron microscope, and an electronic universal testing machine. Results showed that Cu and Er could significantly reduce the grain size of the eutectic Mg₂Si phase from 15.4 µm for the base alloy to 5.8 µm for the alloy with 1.5 wt.% Cu and 0.45 wt.% Er. Meanwhile, the needle-like β-Al₅FeSi phase was modified to fine sized irregular shaped Cu, Er and Fe-rich particles with the additions of Cu and Er. The strength and ductility of the Al-10Mg₂Si as-cast alloys were simultaneously improved by the additions of Cu and Er, and the ultimate tensile strength, yield strength and elongation increase from 223 MPa, 136 MPa and 2.1% to 337 MPa, 169 MPa and 4.7%, respectively. The heterogeneous nucleation of Mg₂Si on AlP was avoided by forming Cu, Er and P-containing phases, due to the additions of Cu and Er. Moreover, the Cu and Er atomic clusters and their intermetallic segregated on the surface of the eutectic Mg₂Si and inhibited the growth of the eutectic Mg₂Si, which were responsible for the modification of the eutectic Mg₂Si.

Keywords

Al-Mg₂Si alloy / Cu / Er / eutectic Mg₂Si / mechanical properties

References

[1] YangX, XiongB, LiX, et al.. Effect of Li addition on mechanical properties and ageing precipitation behavior of extruded Al-3.0Mg-0.5Si alloy [J]. Journal of Central South University, 2021, 28(9): 2636-2646

[2] LiuR, WangW, ChenH. Synthesis of nano-to micrometer-sized B4C particle-reinforced aluminum matrix composites via powder metallurgy and subsequent heat treatment [J]. Journal of Central South University, 2021, 28(8): 2295-2306

[3] JiS, WatsonD, FanZ, et al.. Development of a super ductile diecast Al-Mg-Si alloy [J]. Materials Science and Engineering A, 2012, 556: 824-833

[4] ZhangJ, FanZ, WangY Q, et al.. Equilibrium pseudobinary Al-Mg₂Si phase diagram [J]. Materials Science and Technology, 2001, 17(5): 494-496

[5] LiJ, AnQ, WuS, et al.. Relationship of Mg₂Si morphology with Mg₂Si content and its effect on properties of in situ Mg₂Si/Al-Cu composites [J]. Journal of Alloys and Compounds, 2019, 808: 151771

[6] JiangW, XuX, ZhaoY, et al.. Effect of the addition of Sr modifier in different conditions on microstructure and mechanical properties of T6 treated Al-Mg₂Si in situ composite [J]. Materials Science and Engineering A, 2018, 721263-273

[7] WuX, WangK, WuF, et al.. Simultaneous grain refinement and eutectic Mg₂Si modification in hypoeutectic Al-11Mg₂Si alloys by Sc addition [J]. Journal of Alloys and Compounds, 2019, 791: 402-410

[8] LiC, WangC, MaP, et al.. Effect of Sb modification on microstructure and mechanical properties of hypoeutectic Al-11Mg₂Si alloy [J]. Materials Science and Engineering A, 2020, 782: 139247

[9] WangK, XiangJ, ZhaoR, et al.. Microstructure refinement and enhanced tensile properties of Al-11Mg₂Si alloy modified by erbium [J]. Journal of Alloys and Compounds, 2021, 860158421

[10] DuR, YuanD, LiF, et al.. Effect of in situ TiB₂ particles on microstructure and mechanical properties of Mg₂Si/Al composites [J]. Journal of Alloys and Compounds, 2019, 776536-542

[11] DarlapudiA, McDonaldS D, St JohnD H. The influence of ternary Cu additions on the nucleation of eutectic grains in a hypoeutectic Al-10 wt.% Si alloy [J]. Journal of Alloys and Compounds, 2015, 646: 699-705

[12] LiQ, ZhuY, ZhaoS, et al.. Influences of Fe, Mn and Y additions on microstructure and mechanical properties of hypoeutectic Al-7%Si alloy [J]. Intermetallics, 2020, 120: 106768

[13] KangJ, SuR, WuD Y, et al.. Synergistic effects of Ce and Mg on the microstructure and tensile properties of Al-7Si-0.3Mg-0.2Fe alloy [J]. Journal of Alloys and Compounds, 2019, 796267-278

[14] JosephS, KumarS. A systematic investigation of fracture mechanisms in Al-Si based eutectic alloy—Effect of Si modification [J]. Materials Science and Engineering A, 2013, 588: 111-124

[15] CaoX, CampbellJ. Morphology of β-Al₅FeSi phase in Al-Si cast alloys [J]. Materials Transactions, 2006, 47(5): 1303-1312

[16] ChoY H, LeeH C, OhK H, et al.. Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of β-Al₅FeSi in hypoeutectic Al-Si foundry alloys [J]. Metallurgical and Materials Transactions A, 2008, 39(10): 2435-2448

[17] NogitaK, McDonaldS, TsujimotoK, et al.. Aluminium phosphide as a eutectic grain nucleus in hypoeutectic Al-Si alloys [J]. Journal of Electron Microscopy, 2004, 53(4): 361-369

[18] LiC, WuY Y, LiH, et al.. Morphological evolution and growth mechanism of primary Mg₂Si phase in Al-Mg₂Si alloys [J]. Acta Materialia, 2011, 59(3): 1058-1067

[19] LiJ H, SchumacherP. Effect of Y addition and cooling rate on refinement of eutectic Si in Al-5 wt-%Si alloys [J]. International Journal of Cast Metals Research, 2012, 25(6): 347-357

[20] BarrireroJ, EngstlerM, GhafoorN, et al.. Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy [J]. Journal of Alloys and Compounds, 2014, 611: 410-421

[21] XuC, XiaoW, ZhengR, et al.. The synergic effects of Sc and Zr on the microstructure and mechanical properties of Al-Si-Mg alloy [J]. Materials & Design, 2015, 88: 485-492

[22] LiuW, XiaoW, XuC, et al.. Synergistic effects of Gd and Zr on grain refinement and eutectic Si modification of Al-Si cast alloy [J]. Materials Science and Engineering A, 2017, 693: 93-100

[23] WangF, BhattacharyyaJ J, AgnewS R. Effect of precipitate shape and orientation on Orowan strengthening of non-basal slip modes in hexagonal crystals, application to magnesium alloys [J]. Materials Science and Engineering A, 2016, 666: 114-122

[24] LeoP D G, WalshM J, MaclachlanD, et al.. Crack growth micro-mechanisms in the IN718 alloy under the combined influence of fatigue, creep and oxidation [J]. International Journal of Fatigue, 2009, 31(1112): 1966-1977