Precipitation strengthening in naturally aged Al-Zn-Mg-Cu alloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:803

Article

Lee, Sang-Hwa^1,2  Jung, Jae-Gil^1,3  Baik, Sung-Il^3,4  Seidman, David N.^3,4  Kim, Min-Seok¹  Lee, Young-Kook²  Euh, Kwangjun^1,5 

[1] Korea Inst Mat Sci, Met Mat Div, Chang Won 51508, South Korea

[2] Yonsei Univ, Dept Mat Sci & Engn, Seoul 03722, South Korea

[3] Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA

[4] Northwestern Univ, Ctr Atom Probe Tomog, Evanston, IL 60208 USA

[5] Korea Univ Sci & Technol UST, Adv Mat Engn, Daejeon 34113, South Korea

关键词: Aluminum alloys;    Precipitation;    Mechanical properties;    Transmission electron microscopy;    Misfit strain;    Atom-probe tomography;   

DOI  :  10.1016/j.msea.2020.140719

来源: Elsevier

【 摘 要 】

We investigated the precipitation behavior and mechanical properties of naturally aged Al-7.6Zn-2.7Mg-2.0Cu-0.1Zr-0.07Ti (wt.%) alloy using various experimental methods including electron backscatter diffraction, microhardness, electrical resistivity, differential scanning calorimetry, X-ray diffraction, transmission electron microscopy (TEM), atom-probe tomography (APT), and tensile tests. GPI zones commenced forming after 0.5 h of natural aging and increased in volume fraction during further aging. GPII zones were observed in alloys that were naturally aged longer than 1500 h at 25 degrees C. The APT and TEM analyses identified blocky GPI zones and elongated GPII zones on the {111}(Al) planes in the alloy that were naturally aged for 1500 h. The compressive lattice strains of the GPI and GPII zones were similar to 2.6 and similar to 7.8%, respectively, at the centers of the zones. For the GP zones, the Zn/Mg atomic ratio was similar to 1.2, the mean radius 0.76 nm, the number density 3.22 x 10(24) m(-3), and volume fraction 0.58%. Yield strength modeling, strain hardening behavior, and fractured morphology analyses indicated that the improved strength from natural aging was due to the coherency plus modulus mismatch strengthening of the GP zones, which had an average misfit strain of similar to 4%.

【 授权许可】

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