Reversion of natural ageing and restoration of quick bake-hardening response in Al-Zn-Mg-Cu alloy

Chunhui Liu ¹Zhuangzhuang Feng ¹Peipei Ma ²Yihui Zhou ¹Guohui Li ¹Lihua Zhan¹

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作者信息

1. Light Alloy Research Institute of Central South University,State Key Laboratory of High-Performance Complex Manufacturing,Changsha 410083,China;School of Mechanical and Electrical Engineering,Central South University,Changsha 410083,China
2. Light Alloy Research Institute of Central South University,State Key Laboratory of High-Performance Complex Manufacturing,Changsha 410083,China
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Abstract

The high-strength Al-Zn-Mg-Cu alloy provides much better dent resistance and weight-reduction poten-tial compared to the conventional Al alloys used for the automobile body panels.However,natural age-ing (NA) significantly reduces the formability of Al-Zn-Mg-Cu alloy.The reversion of natural ageing has been systematically investigated by hardness test,tensile test,differential scanning calorimetry (DSC) and transmission electron microscopy (TEM).Substantial reversion of natural ageing and thus hardness de-crease occurs immediately upon thermal treatment at 120-210 ℃ in an Al-Zn-Mg-Cu alloy.Although the hardness of the most reverted state decreases with increasing temperature,the lowest hardness is still higher than the as-quenched state by 30HV.As revealed by the complementary DSC and TEM observa-tions,this is ascribed to the synchronization of the dissolution and the re-precipitation of the solutes in the NA clusters during reversion ageing.Reversion at 180-210 ℃ for less than 30 s leads to a hardness decline of 40HV.The hardening kinetics during NA after reversion is slower than that during first-time NA due to the reduced vacancy concentration.Artificial ageing at 180 ℃ for 30 min after secondary NA of less than 24 h induces intensive precipitation of plate-like pre-ηphases and a giant strength increase of 188-204 MPa.Potential use of high strength Al-Zn-Mg-Cu alloy in automobile body panels could be realized by appropriate reversion treatment improving the formability and the quick bake hardening re-sponse.

Key words

Reversion/Natural ageing/Bake-hardening response/Vacancy/Al-Zn-Mg-Cu alloy

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基金项目

National Natural Science Foundation of China(U2032117)

National Natural Science Foundation of China(51675538)

National Natural Science Foundation of China(11872380)

National Key Research and Development Program of China(2017YFB0306300)

Natural Science Foundation of Hunan Province(2018JJ3655)

National Science and Technology Major Project(2017ZX04005001)

Fundamental Research Funds for the Central Universities of Central South University(2021zzts0638)

Innovation fund of National commercial aircraft manufacturing engineering technology centre(COMAC-SFGS-2019-4284)

出版年

2021

材料科学技术(英文版)

中国金属学会中国材料研究学会中国科学院金属研究所

材料科学技术(英文版)

CSTPCDCSCDSCI

影响因子：0.657

ISSN：1005-0302

参考文献量38

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