首页|Precipitation evolution of Al-Zn-Mg-Cu-(Ag)alloys with a low Zn/Mg ratio

Precipitation evolution of Al-Zn-Mg-Cu-(Ag)alloys with a low Zn/Mg ratio

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The influence of minor Ag on the precipitation evolution of the Al-4.2Zn-2.8Mg-1.0Cu(wt.％)alloy from early stages to over-aged stages at 150 ℃ was investigated.Surprisingly,co-precipitation of strengthening phases T'and η'are found in both Ag-free and Ag-added alloys.With Ag addition,precipitation of both T'and η'is refined and increased,such that the age-hardening capabilities and peak-aged tensile strength are improved.In addition,the quantitative proportion of η'precipitates increases with the increase of Ag content due to the increase in the(Zn+Cu)/Mg ratio of nucleating particles.The narrowed precipitate-free zones(PFZs)are considered responsible for the undiminished fracture elongation in Ag-added alloys.Essentially,these effects of Ag are closely related to the strong Ag-vacancy and Ag-solute interactions.In over-aged stages,the Ag-added alloys still possess higher hardness values compared to the Ag-free al-loy,which is related to precipitate coarsening mechanisms.The Ag-free alloy follows classical coarsening behavior by solid solution mediated diffusion,while the Ag-added alloy follows two possible coarsen-ing mechanisms,coalescence of aggregates and diffusion of atoms.The smaller average size and higher residual number density of precipitates benefited from the slow diffusion-controlled coarsening behavior depending on the precipitate composition characteristics of the two-stage differentiation and the precip-itate distribution characteristics of high-density dispersion in early-aged stages could explain why the hardness of Ag-added alloy keeps at a higher level than that of Ag-free alloy even after 1000 h ageing.Meanwhile,the transformation of metastable phases to stable phases is inhibited due to the addition of Ag,such that GP zones,T',η',η and T phases coexist even after 14 d of ageing.In terms of phase com-position,the addition of Ag decreases the ratio of Mg/(Al+Zn)in T-type phase.For the Ag-added alloy,the sum concentration of Zn+Mg in η'phase is about 10 at.％higher compared to T'phase,and η phase continues to have a high sum concentration of Zn+Mg,besides,the Zn/Mg ratio and Cu concentration exhibit obvious differences from T phase.

Al-Zn-Mg-Cu alloy with low Zn/MgTrace AgCo-precipitationEvolution of precipitationAtom probe tomography

Qianqian Zhu、Xiaodong Wu、Lingfei Cao、Yan Zou、Hui Song、Yahui Liu、Kexing Song、Malcolm J.Couper

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School of Materials Science and Engineering,Henan University of Science and Technology,Luoyang 471023,China

International Joint Laboratory for Light Alloys(Ministry of Education),College of Materials Science and Engineering,Chongqing University,Chongqing 400044,China

School of Mechatronics Engineering,Henan University of Science and Technology,Luoyang 471023,China

Department of Materials Science and Engineering,Monash University,Clayton,VIC,3800,Australia

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Chongqing Key Project for Technological Innovation and ApplicationNatural Science Foundation of ChongqingNational Natural Science Foundation of ChinaOpening Project of State Key Laboratory for Advanced Metals and MaterialsOpening Project of State Key Laboratory for Advanced Metals and Materials

CSTB2022TIAD-KPX0073CSTB2022NSCQ-LZX0002518710332022-Z032020-ZD02

2024

10.1016/j.jmst.2023.12.071

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)

CSTPCD
影响因子：0.657
ISSN：1005-0302
年,卷(期)：2024.195(28)