Effects of dynamic cooling pre-aging treatment on mechanical properties and paint-bake hardening behavior of Al-Mg-Si alloy automotive sheets

Abstract

In the industrial production, the dynamic cooling pre-aging treatment was employed to replace the isothermal pre-aging during the continuous heat treatment production of Al-Mg-Si alloy automotive sheets. The effects of dynamic cooling pre-aging treatment on mechanical properties and paint-bake hardening behavior of an Al-Mg-Si alloy sheet are proposed in this study. The scanning electron microscopy, transmission electron microscopy, tensile test, Vickers hardness test, and differential scanning calorimetry were conducted for the purpose. It was found that the dynamic cooling pre-aging treatment at low temperature region led to the decreasing of cluster II, resulting in the deterioration of the ability of the paint-bake hardening. With the increase of the cooling pre-aging temperature, the increasing of cluster II effectively improved the stability against natural aging and the paint-bake hardening ability. The optimized dynamic cooling pre-aging temperature was ∼150 ° C. In this condition, the hardness increase of the alloy sheet with pre-aging treatment is low during storage at room temperature. The high yield strength increment is obtained after paint-bake hardening.

Keywords

Al-Mg-Si alloy / mechanical properties / paint-bake hardening behavior / dynamic cooling pre-aging / precipitates

References

[1] LuG, WangJ, LiuY, et al.. Effect of heating rate during solution treatment on the bendability of Al-Mg-Si alloys [J]. Materials Science and Engineering A, 2020, 791: 139604

[2] WangD, ShuX, WangR, et al.. Mechanism of necking defect of 6082 aluminium alloy rolled by cross-wedge rolling method based on material thermal properties [J]. Journal of Central South University, 2020, 27(12): 3721-3732

[3] MillerW S, ZhuangL, BottemaJ, et al.. Recent development in aluminium alloys for the automotive industry [J]. Materials Science and Engineering A, 2000, 280(1): 37-49

[4] HirschJ. Aluminium in innovative light-weight car design [J]. Materials Transactions, 2011, 52(5): 818-824

[5] KimK J, RheeM H, ChoiB I, et al.. Development of application technique of aluminum sandwich sheets for automotive hood [J]. International Journal of Precision Engineering and Manufacturing, 2009, 10(4): 71-75

[6] SakuraiT. The latest trends in aluminum alloy sheets for automotive body panels [J]. KOBELCO Technology Review, 2008, 28(28): 22-28

[7] EnglerO, SchäferC, MyhrO R. Effect of natural ageing and pre-straining on strength and anisotropy in aluminium alloy AA6016 [J]. Materials Science and Engineering A, 2015, 63965-74

[8] BirolY. Pre-aging to improve bake hardening in a twin-roll cast Al-Mg-Si alloy [J]. Materials Science and Engineering A, 2005, 391(1–2): 175-180

[9] SerizawaA, HirosawaS, SatoT. Three-dimensional atom probe characterization of nanoclusters responsible for multistep aging behavior of an Al-Mg-Si alloy [J]. Metallurgical and Materials Transactions A, 2008, 39(2): 243-251

[10] GaoG J, LiY, WangZ D, et al.. Interaction between natural aging and pre-aging processes and its impact on the age-hardening behavior of Al-Mg-Si automotive sheets [J]. JOM, 2019, 71(12): 4405-4413

[11] GaoG, HeC, LiY, et al.. Influence of different solution methods on microstructure, precipitation behavior and mechanical properties of Al-Mg-Si alloy [J]. Transactions of Nonferrous Metals Society of China, 2018, 28(5): 839-847

[12] VedaniM, AngellaG, BassaniP, et al.. DSC analysis of strengthening precipitates in ultrafine Al-Mg-Si alloys [J]. Journal of Thermal Analysis and Calorimetry, 2007, 87(1): 277-284

[13] LiuC H, LaiY X, ChenJ H, et al.. Natural-aging-induced reversal of the precipitation pathways in an Al-Mg-Si alloy [J]. Scripta Materialia, 2016, 115: 150-154

[14] TaoG H, LiuC H, ChenJ H, et al.. The influence of Mg/Si ratio on the negative natural aging effect in Al-Mg-Si-Cu alloys [J]. Materials Science and Engineering A, 2015, 642: 241-248

[15] CaoL, RometschP A, CouperM J. Clustering behaviour in an Al-Mg-Si-Cu alloy during natural ageing and subsequent under-ageing [J]. Materials Science and Engineering A, 2013, 559: 257-261

[16] YuanB, GuoM, WuY, et al.. Influence of treatment pathways on the precipitation behaviors of Al-Mg-Si-Cu-(Zn)-Mn alloys [J]. Journal of Alloys and Compounds, 2019, 797: 26-38

[17] LayM D H, ZurobH S, HutchinsonC R, et al.. Vacancy behavior and solute cluster growth during natural aging of an Al-Mg-Si alloy [J]. Metallurgical and Materials Transactions A, 2012, 43(12): 4507-4513

[18] MadanatM, LiuM, BanhartJ. Reversion of natural ageing in Al-Mg-Si alloys [J]. Acta Materialia, 2018, 159: 163-172

[19] DingL, JiaZ, LiuY, et al.. The influence of Cu addition and pre-straining on the natural aging and bake hardening response of Al-Mg-Si alloys [J]. Journal of Alloys and Compounds, 2016, 688: 362-367

[20] KwonY N, LeeY S, LeeJ H. Deformation behavior of Al-Mg-Si alloy at the elevated temperature [J]. Journal of Materials Processing Technology, 2007, 187–188: 533-536

[21] WuW, SiC. Investigation of electrical pulse induced retrogression and restoration effect of Al-Mg-Si alloy [J]. Science of Advanced Materials, 2017, 9(9): 1662-1668

[22] FallahV, LangelierB, Ofori-OpokuN, et al.. Cluster evolution mechanisms during aging in Al-Mg-Si alloys [J]. Acta Materialia, 2016, 103: 290-300

[23] HuangK, MarthinsenK, ZhaoQ, et al.. The double-edge effect of second-phase particles on the recrystallization behaviour and associated mechanical properties of metallic materials [J]. Progress in Materials Science, 2018, 92: 284-359

[24] LiH, YanZ, CaoL. Bake hardening behavior and precipitation kinetic of a novel Al-Mg-Si-Cu aluminum alloy for lightweight automotive body [J]. Materials Science and Engineering A, 2018, 728: 88-94

[25] AbidT, BoubertakhA, HamamdaS. Effect of preaging and maturing on the precipitation hardening of an Al-Mg-Si alloy [J]. Journal of Alloys and Compounds, 2010, 490(1–2): 166-169

[26] YangZ, LiangZ, LeyvrazD, et al.. Effect of preageing on natural secondary ageing and paint bake hardening in Al-Mg-Si alloys [J]. Materialia, 2019, 7100413

[27] de HaasM, de HossonJ T M. On the effects of thermomechanical processing on failure mode in precipitation-hardened aluminium alloys [J]. Journal of Materials Science, 2002, 37(23): 5065-5073