Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

Abstract

In the present work, scandium elements with a series of contents (0.06 wt.%, 0.10 wt.%, 0.14 wt.%, 0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn₂ phases discontinuously distributed on them. Besides, AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.

Keywords

Al-Zn-Mg-Cu-Zr alloy / high zinc content / microstructure / Sc addition / grain refinement / phase evolution

References

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

[2] RaoA C U, VasuV, GovindarajuM, et al.. Stress corrosion cracking behaviour of 7xxx aluminum alloys: A literature review [J]. Transactions of Nonferrous Metals Society of China, 2016, 26(6): 1447-1471

[3] RometschP A, ZhangY, KnightS. Heat treatment of 7xxx series aluminium alloys—Some recent developments [J]. Transactions of Nonferrous Metals Society of China, 2014, 24(7): 2003-2017

[4] AzarniyaA, TaheriA K, TaheriK K. Recent advances in ageing of 7xxx series aluminum alloys: A physical metallurgy perspective [J]. Journal of Alloys and Compounds, 2019, 781: 945-983

[5] WeiS, FengY, ZhangH, et al.. Influence of aging on microstructure, mechanical properties and stress corrosion cracking of 7136 aluminum alloy [J]. Journal of Central South University, 2021, 28: 2687-2700

[6] HeK, LiQ, LiuS, et al.. Influence of pre-stretching on quench sensitive effect of high-strength Al-Zn-Mg-Cu-Zr alloy sheet [J]. Journal of Central South University, 2021, 28: 2660-2669

[7] LiuJ, ZhangY, LiX, et al.. Phases and microstructures of high Zn-containing Al-Zn-Mg-Cu alloys [J]. Rare Metals, 2016, 35(5): 380-384

[8] WenK, FanY, WangG, et al.. Aging behavior and fatigue crack propagation of high Zn-containing Al-Zn-Mg-Cu alloys with zinc variation [J]. Progress in Natural Science: Materials International, 2017, 27(2): 217-227

[9] ChenC, HanW, QiM, et al.. Microstructural evolution and mechanical properties of an ultrahigh-strength Al-Zn-Mg-Cu alloy via powder metallurgy and hot extrusion [J]. Journal of Central South University, 2021, 28: 1195-1205

[10] LiH, CaoF, GuoS, et al.. Effects of Mg and Cu on microstructures and properties of spray-deposited Al-Zn-Mg-Cu alloys [J]. Journal of Alloys and Compounds, 2017, 719: 89-96

[11] DongP, ChenS, ChenK. Effects of Cu content on microstructure and properties of super-high-strength Al-9.3Zn-2.4Mg-xCu-Zr alloy [J]. Journal of Alloys and Compounds, 2019, 788: 329-337

[12] LiaoY, HanX, ZengM, et al.. Influence of Cu on microstructure and tensile properties of 7XXX series aluminum alloy [J]. Materials & Design, 2015, 66: 581-586

[13] ZhaoQ, QianZ, CuiX, et al.. Influences of Fe, Si and homogenization on electrical conductivity and mechanical properties of dilute Al-Mg-Si alloy [J]. Journal of Alloys and Compounds, 2016, 666: 50-57

[14] CurleU A, CornishL A, GovenderG. Predicting yield strengths of Al-Zn-Mg-Cu-(Zr) aluminium alloys based on alloy composition or hardness [J]. Materials & Design, 2016, 99: 211-218

[15] WuH, WenS, LuJ, et al.. Microstructural evolution of new type Al-Zn-Mg-Cu alloy with Er and Zr additions during homogenization [J]. Transactions of Nonferrous Metals Society of China, 2017, 27(7): 1476-1482

[16] WuH, WenS P, HuangH, et al.. Effects of homogenization on precipitation of Al₃(Er, Zr) particles and recrystallization behavior in a new type Al-Zn-Mg-Er-Zr alloy [J]. Materials Science and Engineering A, 2017, 689: 313-322

[17] LiB, PanQ, ChenC, et al.. Effects of solution treatment on microstructural and mechanical properties of Al-Zn-Mg alloy by microalloying with Sc and Zr [J]. Journal of Alloys and Compounds, 2016, 664: 553-564

[18] YoganjaneyuluG, BabuK A, VigneshwaranS, et al.. Microstructure and mechanical properties of cryorolled Al-6Zn-3Mg-2Cu-0.5Sc alloy [J]. Materials Letters, 2019, 253: 18-21

[19] EivaniA R, AhmedH, ZhouJ, et al.. An experimental and theoretical investigation of the formation of Zr-containing dispersoids in Al-4.5Zn-1Mg aluminum alloy [J]. Materials Science and Engineering A, 2010, 527(9): 2418-2430

[20] LiaoZ, LiS, ZhengZ, et al.. The effect of Ge addition on Al-3.5Cu-0.4Mg (wt.%) alloy [J]. Scripta Materialia, 2012, 66(7): 447-450

[21] OkleP, LinJ D, ZhuT, et al.. Effect of microadditions of Ge, In or Sn on precipitation in dilute Al-Sc-Zr alloys [J]. Materials Science and Engineering A, 2019, 739: 427-436

[22] ChenY, LiuC Y, ZhangB, et al.. Effects of friction stir processing and minor Sc addition on the microstructure, mechanical properties, and damping capacity of 7055 Al alloy [J]. Materials Characterization, 2018, 135: 25-31

[23] LiJ H, WiessnerM, AlbuM, et al.. Correlative characterization of primary Al₃(Sc, Zr) phase in an Al-Zn-Mg based alloy [J]. Materials Characterization, 2015, 102: 62-70

[24] LiuC, TengG, MaZ, et al.. Effects of Sc and Zr microalloying on the microstructure and mechanical properties of high Cu content 7xxx Al alloy [J]. International Journal of Minerals, Metallurgy and Materials, 2019, 26(12): 1559-1569

[25] RogalL, DutkiewiczJ, AtkinsonH V, et al.. Characterization of semi-solid processing of aluminium alloy 7075 with Sc and Zr additions [J]. Materials Science and Engineering A, 2013, 580: 362-373

[26] DengY, YinZ, ZhaoK, et al.. Effects of Sc and Zr microalloying additions on the microstructure and mechanical properties of new Al-Zn-Mg alloys [J]. Journal of Alloys and Compounds, 2012, 530: 71-80

[27] LiuJ, YaoP, ZhaoN, et al.. Effect of minor Sc and Zr on recrystallization behavior and mechanical properties of novel Al-Zn-Mg-Cu alloys [J]. Journal of Alloys and Compounds, 2016, 657: 717-725

[28] ZhangM, LiuT, HeC, et al.. Evolution of microstructure and properties of Al-Zn-Mg-Cu-Sc-Zr alloy during aging treatment [J]. Journal of Alloys and Compounds, 2016, 658: 946-951

[29] SenkovO N, BhatR B, SenkovaS V, et al.. Microstructure and properties of cast ingots of Al-Zn-Mg-Cu alloys modified with Sc and Zr [J]. Metallurgical and Materials Transactions A, 2005, 36(8): 2115-2126

[30] LiuL, JiaY, JiangJ, et al.. The effect of Cu and Sc on the localized corrosion resistance of Al-Zn-Mg-X alloys [J]. Journal of Alloys and Compounds, 2019, 799: 1-14

[31] LiH, CaoF, GuoS, et al.. Microstructures and properties evolution of spray-deposited Al-Zn-Mg-Cu-Zr alloys with scandium addition [J]. Journal of Alloys and Compounds, 2017, 691: 482-488

[32] ZhouL, PanH, HyerH, et al.. Microstructure and tensile property of a novel AlZnMgScZr alloy additively manufactured by gas atomization and laser powder bed fusion [J]. Scripta Materialia, 2019, 158: 24-28

[33] TengG B, LiuC Y, MaZ Y, et al.. Effects of minor Sc addition on the microstructure and mechanical properties of 7055 Al alloy during aging [J]. Materials Science and Engineering A, 2018, 713: 61-66

[34] WuL, WangW H, HsuY F, et al.. Effects of homogenization treatment on recrystallization behavior and dispersoid distribution in an Al-Zn-Mg-Sc-Zr alloy [J]. Journal of Alloys and Compounds, 2008, 456(12): 163-169

[35] DengY, YeR, XuG, et al.. Corrosion behaviour and mechanism of new aerospace Al-Zn-Mg alloy friction stir welded joints and the effects of secondary Al₃Sc_xZr_1−x nanoparticles [J]. Corrosion Science, 2015, 90: 359-374

[36] HuangX, PanQ, LiB, et al.. Microstructure, mechanical properties and stress corrosion cracking of Al-Zn-Mg-Zr alloy sheet with trace amount of Sc [J]. Journal of Alloys and Compounds, 2015, 650: 805-820

[37] WangG, ZhaoZ, ZhangY, et al.. Effects of solution treatment on microstructure and mechanical properties of Al-9.0Zn-2.8Mg-2.5Cu-0.12Zr-0.03Sc alloy [J]. Transactions of Nonferrous Metals Society of China, 2013, 23(9): 2537-2542

[38] RenJ, WangR, FengY, et al.. Microstructure evolution and mechanical properties of an ultrahigh strength Al-Zn-Mg-Cu-Zr-Sc (7055) alloy processed by modified powder hot extrusion with post aging [J]. Vacuum, 2019, 161: 434-442

[39] CostaS, PugaH, BarbosaJ, et al.. The effect of Sc additions on the microstructure and age hardening behaviour of as cast Al-Sc alloys [J]. Materials & Design, 2012, 42: 347-352

[40] VlachM, CizekJ, KodetovaV, et al.. Phase transformations in novel hot-deformed Al-Zn-Mg-Cu-Si-Mn-Fe (-Sc-Zr) alloys [J]. Materials & Design, 2020, 193: 108821

[41] VlachM, KodetovaV, CizekJ, et al.. Role of small addition of Sc and Zr in clustering and precipitation phenomena induced in AA7075 [J]. Metals, 2020, 11(1): 8

[42] VlachM, CížekJ, KodetováV, et al.. Annealing effects in cast commercial aluminium Al-Mg-Zn-Cu (-Sc-Zr) alloys [J]. Metals and Materials International, 2021, 275995-1004

[43] ManoharP A, FerryM, ChandraT. Five decades of the zener equation [J]. ISIJ International, 1998, 38(9): 913-924

[44] ZhouS, ZhangZ, LiM, et al.. Effect of Sc on microstructure and mechanical properties of as-cast Al-Mg alloys [J]. Materials & Design, 2016, 901077-1084

[45] ZhouS, ZhangZ, LiM, et al.. Correlative characterization of primary particles formed in as-cast Al-Mg alloy containing a high level of Sc [J]. Materials Characterization, 2016, 118: 85-91

[46] TrudonoshynO, PrachO. Multistep nucleation and multi-modification effect of Sc in hypoeutectic Al-Mg-Si alloys [J]. Heliyon, 2019, 52e01202