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<p>Al-Zn-Mg-Cu alloys are heat-treatable materials whose microstructure and properties are highly sensitive to solution treatment schedules. In this study, WAAM-deposited Al-6.63Zn-1.4&#xa0;Mg-1.19Cu-0.021Sr-0.21Zr-0.14Ti-0.15Er alloy was systematically investigated to clarify the effects of single-stage and multistage solution treatments in additively manufactured 7xxx alloys. Four solution treatment schedules were designed: two single-stage treatments (G1:470&#xa0;°C × 2&#xa0;h; G2:470&#xa0;°C × 6 h) and two multistage treatments (G3:450&#xa0;°C × 2&#xa0;h + 460&#xa0;°C × 2&#xa0;h + 470&#xa0;°C × 2&#xa0;h; G4:450 °C × 2&#xa0;h + 460&#xa0;°C × 2&#xa0;h + 470&#xa0;°C × 2&#xa0;h + 475&#xa0;°C × 2&#xa0;h), followed by T6 peak aging. Optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD), electron backscatter diffraction (EBSD), hardness, electrical conductivity, tensile testing, and multiple corrosion tests were employed to evaluate the microstructural evolution and corresponding property variations. The results indicate that the three-stage solution treatment (G3) leads to pronounced grain refinement (average grain size: 30.48&#xa0;μm), reduced porosity, and relatively fine and uniformly distributed <i>η</i> (MgZn<sub>2</sub>) and S (Al<sub>2</sub>CuMg) precipitates. Consequently, the G3 specimen exhibits a favorable strength-ductility synergy (ultimate tensile strength of 493.93&#xa0;MPa and elongation of 13.73%) together with improved corrosion resistance (intergranular corrosion depth of 28.43&#xa0;μm, exfoliation corrosion rating PB, and corrosion potential of − 0.98485&#xa0;V). Although the prolonged single-stage treatment (G2) achieves the highest tensile strength (516.83&#xa0;MPa), it shows inferior ductility and corrosion resistance. In comparison, the G1 and G4 conditions provide relatively less balanced overall performance. These findings suggest that a three-stage solution treatment offers an effective strategy to achieve a balanced enhancement of strength, ductility, and corrosion resistance in WAAM-fabricated 7xxx aluminum alloys.</p>

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Effect of Heat Treatment on the Microstructure and Overall Performance of 7xxx Series Aluminum Alloy Welding Wire-Deposited Components

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • Yunjie Liu,
  • Yu Li,
  • Deli Kong,
  • Xiaojing Xu

摘要

Al-Zn-Mg-Cu alloys are heat-treatable materials whose microstructure and properties are highly sensitive to solution treatment schedules. In this study, WAAM-deposited Al-6.63Zn-1.4 Mg-1.19Cu-0.021Sr-0.21Zr-0.14Ti-0.15Er alloy was systematically investigated to clarify the effects of single-stage and multistage solution treatments in additively manufactured 7xxx alloys. Four solution treatment schedules were designed: two single-stage treatments (G1:470 °C × 2 h; G2:470 °C × 6 h) and two multistage treatments (G3:450 °C × 2 h + 460 °C × 2 h + 470 °C × 2 h; G4:450 °C × 2 h + 460 °C × 2 h + 470 °C × 2 h + 475 °C × 2 h), followed by T6 peak aging. Optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD), electron backscatter diffraction (EBSD), hardness, electrical conductivity, tensile testing, and multiple corrosion tests were employed to evaluate the microstructural evolution and corresponding property variations. The results indicate that the three-stage solution treatment (G3) leads to pronounced grain refinement (average grain size: 30.48 μm), reduced porosity, and relatively fine and uniformly distributed η (MgZn2) and S (Al2CuMg) precipitates. Consequently, the G3 specimen exhibits a favorable strength-ductility synergy (ultimate tensile strength of 493.93 MPa and elongation of 13.73%) together with improved corrosion resistance (intergranular corrosion depth of 28.43 μm, exfoliation corrosion rating PB, and corrosion potential of − 0.98485 V). Although the prolonged single-stage treatment (G2) achieves the highest tensile strength (516.83 MPa), it shows inferior ductility and corrosion resistance. In comparison, the G1 and G4 conditions provide relatively less balanced overall performance. These findings suggest that a three-stage solution treatment offers an effective strategy to achieve a balanced enhancement of strength, ductility, and corrosion resistance in WAAM-fabricated 7xxx aluminum alloys.