Mechanical properties and microstructure of as-cast AA7050 processed by equal channel angular pressing combined with inter-pass aging treatment

Abstract

In this study, the interaction between deformation and precipitates during multiple equal channel angular pressing (ECAP) deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied. The result show that ECAP induces numerous substructures and dislocations, effectively promoting the precipitation of the η′ phase exhibiting a bimodal structure during inter-pass aging. Following inter-pass aging and subsequent ECAP, the decrease in grain size (4.8 µm) is together with the increase in dislocation density (1.24×10¹⁵ m⁻²) due to the pinning effect of the precipitated phase. Simultaneously, the dislocation motion causes the second phase particles to become even finer and more diffuse. The synergistic effects of precipitation strengthening, fine grain strengthening, and dislocation strengthening collectively enhance the high strength of aluminum alloys, with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa, respectively. Meanwhile, ductility remains largely unchanged, primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.

Keywords

equal channel angular pressing / 7050 aluminum alloys / inter-pass aging / mechanical properties / precipitates / dislocation

References

[1] GaoJ-y, HeT, HuoY-m, et al.. Comparison of modified Mohr-Coulomb model and Bai-Wierzbicki model for constructing 3D ductile fracture envelope of AA6063 [J]. Chinese Journal of Mechanical Engineering, 2021, 34(1): 35

[2] SenatorovaO G, UksusnikovA N, LegoshinaS F, et al.. Influence of different minor additions on structure and properties of high-strength Al-Zn-Mg-Cu alloy sheets [J]. Materials Science Forum, 2000, 331–337: 1249-1254

[3] JiaD-s, HeT, SongM, et al.. Microstructure evolution of 7050 Al alloy fasteners during cold upsetting after equal channel angular pressing [J]. Journal of Central South University, 2023, 30(11): 3682-3695

[4] LiJ, HeT, DuX-y, et al.. Enhancing the corrosion resistance of high-strength Al-Zn-Mg-Cu alloys after equal channel angular pressing by developing retrogression and re-aging strategies [J]. Corrosion Science, 2025, 246: 112736

[5] HouL G, YuH, WangY W, et al.. Tailoring precipitation/properties and related mechanisms for a high-strength aluminum alloy plate via low-temperature retrogression and re-aging processes [J]. Journal of Materials Science & Technology, 2022, 120: 15-35

[6] LiuP, HuL-l, ZhangQ-h, et al.. Effect of aging treatment on microstructure and corrosion behavior of Al-Zn-Mg aluminum alloy in aqueous solutions with different aggressive ions [J]. Journal of Materials Science & Technology, 2021, 64: 85-98

[7] MoY-t, WangC, ZhangS-y, et al.. Achieving high strength-ductility synergy through high-density coherent precipitation in twin-roll cast Al-Zn-Mg-Cu strips [J]. Materials Science and Engineering A, 2022, 850: 143592

[8] WangZ-p, GengJ-w, PuQ-q, et al.. Achieving high performance by optimized heat treatment in a spray formed Al-Zn-Mg-Cu alloy [J]. Materials Science and Engineering A, 2024, 893: 146134

[9] RojasJ I, CrespoD. Dynamic microstructural evolution of an Al-Zn-Mg-Cu alloy (7075) during continuous heating and the influence on the viscoelastic response [J]. Materials Characterization, 2017, 134: 319-328

[10] SegalV M. Materials processing by simple shear [J]. Materials Science and Engineering A, 1995, 197(2): 157-164

[11] KumarS R, GudimetlaK, VenkatachalamP, et al.. Microstructural and mechanical properties of Al7075 alloy processed by equal channel angular pressing [J]. Materials Science and Engineering A, 2012, 533: 50-54

[12] TolaminejadB, DehghaniK. Microstructural characterization and mechanical properties of nanostructured AA1070 aluminum after equal channel angular extrusion [J]. Materials & Design, 2012, 34: 285-292

[13] NejadseyfiO, ShokuhfarA, DabiriA, et al.. Combining equal-channel angular pressing and heat treatment to obtain enhanced corrosion resistance in 6061 aluminum alloy [J]. Journal of Alloys and Compounds, 2015, 648: 912-918

[14] LiJ, HeT, DuX-y, et al.. Regulating hardness homogeneity and corrosion resistance of Al-Zn-Mg-Cu alloy via ECAP combined with inter-pass aging [J]. Materials Characterization, 2024, 218: 114489

[15] DuanY-l, TangL, XuG-f, et al.. Microstructure and mechanical properties of 7005 aluminum alloy processed by room temperature ECAP and subsequent annealing [J]. Journal of Alloys and Compounds, 2016, 664: 518-529

[16] JiangJ-y, ChenH-w, CaoX-h, et al.. Microstructure, mechanical property and thermo-stability of traditionally and severely deformed Al-Mg-Sc-Zr alloy [J]. Journal of Materials Research and Technology, 2022, 18: 4130-4144

[17] GaoY, GuoT-b, FengR, et al.. High strength high conductivity copper prepared by C-ECAP and cryorolling [J]. Materials Characterization, 2024, 208: 113665

[18] CardosoK R, TravessaD N, BottaW J, et al.. High strength AA7050 Al alloy processed by ECAP: Microstructure and mechanical properties [J]. Materials Science and Engineering A, 2011, 528(18): 5804-5811

[19] LiG-s, XuS-k, WanT-j, et al.. Effect of intermediate-temperature severe plastic deformation on microstructure evolution, mechanical properties and corrosion behavior of an Al-Zn-Mg-Cu alloy [J]. Materials Characterization, 2023, 205: 113248

[20] ChenL, HouY-z, LiZ-g, et al.. Enhancing mechanical properties and corrosion resistance of a high strength 7A99 Al alloy by introducing pre-rolling in solution and aging treatments [J]. Journal of Alloys and Compounds, 2022, 898: 162972

[21] WangW-y, PanQ-l, WangX-d, et al.. Mechanical properties and microstructure evolution of ultrahigh strength Al-Zn-Mg-Cu alloy processed by room temperature ECAP with post aging [J]. Materials Science and Engineering A, 2018, 731: 195-208

[22] DadbakhshS, Karimi TaheriA, SmithC W. Strengthening study on 6082 Al alloy after combination of aging treatment and ECAP process [J]. Materials Science and Engineering A, 2010, 527(1819): 4758-4766

[23] FritschS, WagnerM. On the effect of natural aging prior to low temperature ECAP of a high-strength aluminum alloy [J]. Metals, 2018, 8(1): 63

[24] JiaD-s, HeT, SongM, et al.. Effects of equal channel angular pressing and further cold upsetting process to the kinetics of precipitation during aging of 7050 aluminum alloy [J]. Journal of Materials Research and Technology, 2023, 26: 5126-5140

[25] ChenY-m, WuY-n, GengJ, et al.. Pre-precipitating promoted by microshear bands effectively circumvents strength-ductility trade-off of RT-rolled Al-6Zn-1Mg alloy [J]. Journal of Materials Research and Technology, 2024, 28: 2767-2777

[26] JiangF-q, TangL, HuangJ-w, et al.. Influence of equal channel angular pressing on the evolution of microstructures, aging behavior and mechanical properties of as-quenched Al-6.6Zn-1.25Mg alloy [J]. Materials Characterization, 2019, 153: 1-13

[27] YaoJ-j, ZhangD, GengY-x, et al.. Regulating microstructure of novel Al-Mg-Zn alloy for enhancing comprehensive performance through retrogression and thermo-mechanical treatment [J]. Materials Characterization, 2023, 202: 113000

[28] AshrafizadehS M, EivaniA R, JafarianH R, et al.. Improvement of mechanical properties of AA6063 aluminum alloy after equal channel angular pressing by applying a two-stage solution treatment [J]. Materials Science and Engineering A, 2017, 687: 54-62

[29] XiongH-q, ZhouY-x, YangP, et al.. Effects of cryorolling, room temperature rolling and aging treatment on mechanical and corrosion properties of 7050 aluminum alloy [J]. Materials Science and Engineering A, 2022, 853: 143764

[30] AfifiM A, PereiraP H R, WangY-c, et al.. Effect of ECAP processing on microstructure evolution and dynamic compressive behavior at different temperatures in an Al-Zn-Mg alloy [J]. Materials Science and Engineering A, 2017, 684: 617-625

[31] UngárT, BorbélyA. The effect of dislocation contrast on X-ray line broadening: A new approach to line profile analysis [J]. Applied Physics Letters, 1996, 69(21): 3173-3175

[32] SimmT H, WithersP J, Quinta Da FonsecaJ. An evaluation of diffraction peak profile analysis (DPPA) methods to study plastically deformed metals [J]. Materials & Design, 2016, 111: 331-343

[33] ZHANG Jun-jie, HE Tao, DU Xiang-yang, et al. Effect of pre-equal channel angular pressing homogenization on microstructure and mechanical properties of as-cast 7050 Al alloy [J]. Journal of Materials Engineering and Performance, 2024. DOI: https://doi.org/10.1007/s11665-024-09950-1.

[34] LiM H, YangY Q, FengZ Q, et al.. Influence of equal-channel angular pressing on aging precipitation in 7050 Al alloy [J]. Intermetallics, 2014, 55: 49-55

[35] HuT, MaK, ToppingT D, et al.. Precipitation phenomena in an ultrafine-grained Al alloy [J]. Acta Materialia, 2013, 61(6): 2163-2178

[36] Amin-AhmadiB, PauzaJ G, ShamimiA, et al.. Coherency strains of H-phase precipitates and their influence on functional properties of nickel-titanium-hafnium shape memory alloys [J]. Scripta Materialia, 2018, 147: 83-87

[37] GubiczaJ, SchillerI, ChinhN Q, et al.. The effect of severe plastic deformation on precipitation in supersaturated Al-Zn-Mg alloys [J]. Materials Science and Engineering A, 2007, 460: 77-85

[38] ZhangT, HouY-z, QueB-h, et al.. Combining pre-rolling with retrogression and re-aging treatment to balance strength and corrosion resistance of 7A99 Al alloy [J]. Transactions of Nonferrous Metals Society of China, 2023, 33(10): 2913-2925

[39] AfifiM A, WangY-c, PereiraP H R, et al.. Characterization of precipitates in an Al-Zn-Mg alloy processed by ECAP and subsequent annealing [J]. Materials Science and Engineering A, 2018, 712: 146-156

[40] LinL-h, LiuZ-y, ZhuangW-w, et al.. Effects of pre-strain on the surface residual stress and corrosion behavior of an Al-Zn-Mg-Cu alloy plate [J]. Materials Characterization, 2020, 160: 110129

[41] DongQ-s, HowellsA, GallerneaultM F, et al.. Precipitation-induced mitigation of recrystallization in ultra-thin, cold-rolled AlScZrMn(Mg) sheets at brazing temperatures: The critical effect of alloy composition and thermal processing route [J]. Acta Materialia, 2020, 186: 308-323

[42] MaP-p, LiuC-h, ChenQ-y, et al.. Natural-ageing-enhanced precipitation near grain boundaries in high-strength aluminum alloy [J]. Journal of Materials Science & Technology, 2020, 46: 107-113

[43] ZhangS, HuW, BerghammerR, et al.. Microstructure evolution and deformation behavior of ultrafine-grained Al-Zn-Mg alloys with fine η′ precipitates [J]. Acta Materialia, 2010, 58(20): 6695-6705

[44] MaK-k, WenH-m, HuT, et al.. Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy [J]. Acta Materialia, 2014, 62: 141-155

[45] MaK-k, HuT, YangH, et al.. Coupling of dislocations and precipitates: Impact on the mechanical behavior of ultrafine grained Al-Zn-Mg alloys [J]. Acta Materialia, 2016, 103: 153-164

[46] InjorO M, DaramolaO O, AdewuyiB O, et al.. Grain refinement of Al-Zn-Mg alloy during equal channel angular pressing (ECAP) [J]. Results in Engineering, 2022, 16: 100739

[47] TangL, PengX-y, JiangF-q, et al.. Strong and ductile Al-Zn-Mg-Zr alloy obtained by equal angular pressing and subsequent aging [J]. Transactions of Nonferrous Metals Society of China, 2022, 32(5): 1428-1441

[48] LuoL, YangB-h, YangX-r, et al.. Effect of room temperature multi-pass ECAP deformation on mechanical properties and precipitation phase distribution of 7075 aluminium alloy [J]. Journal of Central South University, 2023, 30(2): 374-386

[49] HockaufK, WagnerM F X, HalleT, et al.. Influence of precipitates on low-cycle fatigue and crack growth behavior in an ultrafine-grained aluminum alloy [J]. Acta Materialia, 2014, 80: 250-263

RIGHTS & PERMISSIONS

Central South University