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

Sang Hwa Lee, Jae Gil Jung, Sung Il Baik, David N. Seidman, Min Seok Kim, Young Kook Lee, Kwangjun Euh

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3 Citations (Scopus)

Abstract

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 °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 ~2.6 and ~7.8%, respectively, at the centers of the zones. For the GP zones, the Zn/Mg atomic ratio was ~1.2, the mean radius 0.76 nm, the number density 3.22 × 1024 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 ~4%.

Original languageEnglish
Article number140719
JournalMaterials Science and Engineering A
Volume803
DOIs
Publication statusPublished - 2021 Jan 28

Bibliographical note

Funding Information:
This work was supported by the Industrial Strategic Technology Development Program (10062304) funded by the Ministry of Trade, Industry & Energy (MOTIE, Republic of Korea) and National R&D program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (2020M3H4A3106328). Atom-probe tomography was performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT). The LEAP tomograph at NUCAPT was purchased and upgraded with grants from the NSF-MRI (DMR-0420532) and ONRDURIP (N00014-0400798, N00014-0610539, N00014-0910781, N00014-1712870) programs. NUCAPT received support from the MRSEC program (NSF DMR-1720139) at the Materials Research Center, the SHyNE Resource (NSF ECCS-1542205), and the Initiative for Sustainability and Energy (ISEN) at Northwestern University. We thank Prof. Dieter Isheim, Dr. Amir Farkoosh and Dr. Richard Michi for helpful discussions concerning APT analyses, and Dr. Tae-Young Ahn for his help with the TEM analyses.

Funding Information:
This work was supported by the Industrial Strategic Technology Development Program ( 10062304 ) funded by the Ministry of Trade, Industry & Energy (MOTIE , Republic of Korea) and National R&D program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT ( 2020M3H4A3106328 ). Atom-probe tomography was performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT) . The LEAP tomograph at NUCAPT was purchased and upgraded with grants from the NSF- MRI ( DMR-0420532 ) and ONRDURIP ( N00014-0400798 , N00014-0610539 , N00014-0910781 , N00014-1712870 ) programs. NUCAPT received support from the MRSEC program ( NSF DMR-1720139 ) at the Materials Research Center, the SHyNE Resource ( NSF ECCS-1542205 ), and the Initiative for Sustainability and Energy (ISEN) at Northwestern University . We thank Prof. Dieter Isheim, Dr. Amir Farkoosh and Dr. Richard Michi for helpful discussions concerning APT analyses, and Dr. Tae-Young Ahn for his help with the TEM analyses.

Publisher Copyright:
© 2020 Elsevier B.V.

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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