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<p>The oxidation behavior of AlCoCrFeNiCu<sub>0.5</sub> high-entropy alloy (HEA) in air at both 800&#xa0;°C and 900&#xa0;°C has been analyzed and corresponding microstructural evolution after oxidation has also been studied. The experimental studies revealed that the as-cast AlCoCrFeNiCu<sub>0.5</sub> alloy is mainly composed of BCC and FCC phases, moreover, there is a spinodal structure with the constituent phases being NiAl-B2 and FeCr-BCC. After annealing at 900&#xa0;°C for 6&#xa0;h, the spinodal structure disappeared, but there was σ phase at grain boundary. Oxidation caused significant changes in the matrix of the alloy. The primary phases of the oxidized matrix are the NiAl-B2 phase and FeCoCr-FCC1 phase. A substantial amount of Al was consumed in matrix to form Al<sub>2</sub>O<sub>3</sub> on the surface, resulting in the formation of Al-depleted layer. The longer the oxidation time, the thicker the Al-depleted layer, and a concentrated distribution of Cu-rich FCC2 phase was observed in this region. The isothermal oxidation kinetics of the alloy at both 800&#xa0;°C and 900&#xa0;°C followed the parabolic law. The <i>k</i><sub>p</sub> values for oxidation at 800&#xa0;°C and 900&#xa0;°C were 7.367 × 10<sup>− 14</sup> (g<sup>2</sup>·cm<sup>− 4</sup>·s<sup>− 1</sup>) and 2.105 × 10<sup>− 13</sup> (g<sup>2</sup>·cm<sup>− 4</sup>·s<sup>− 1</sup>) respectively, indicating that the <i>k</i><sub>p</sub> value at 900&#xa0;°C was 2.86 times that at 800&#xa0;°C. A continuous Al<sub>2</sub>O<sub>3</sub> layer on the surface being the key to its superior oxidation resistance of the HEA at both temperatures.</p> Graphical Abstract <p></p>

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Oxidation Behavior of the AlCoCrFeNiCu0.5 High-Entropy Alloy at 800 °C and 900 °C

  • 期刊论文

  • 发表日期：

    2025年1月9日

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  • Xu Chen,
  • Qihan Li,
  • Ye Liu,
  • Lin Zhang,
  • Shuang He,
  • Oleg I. Gorbatov,
  • Xuanhui Qu

摘要

The oxidation behavior of AlCoCrFeNiCu0.5 high-entropy alloy (HEA) in air at both 800 °C and 900 °C has been analyzed and corresponding microstructural evolution after oxidation has also been studied. The experimental studies revealed that the as-cast AlCoCrFeNiCu0.5 alloy is mainly composed of BCC and FCC phases, moreover, there is a spinodal structure with the constituent phases being NiAl-B2 and FeCr-BCC. After annealing at 900 °C for 6 h, the spinodal structure disappeared, but there was σ phase at grain boundary. Oxidation caused significant changes in the matrix of the alloy. The primary phases of the oxidized matrix are the NiAl-B2 phase and FeCoCr-FCC1 phase. A substantial amount of Al was consumed in matrix to form Al2O3 on the surface, resulting in the formation of Al-depleted layer. The longer the oxidation time, the thicker the Al-depleted layer, and a concentrated distribution of Cu-rich FCC2 phase was observed in this region. The isothermal oxidation kinetics of the alloy at both 800 °C and 900 °C followed the parabolic law. The kp values for oxidation at 800 °C and 900 °C were 7.367 × 10− 14 (g2·cm− 4·s− 1) and 2.105 × 10− 13 (g2·cm− 4·s− 1) respectively, indicating that the kp value at 900 °C was 2.86 times that at 800 °C. A continuous Al2O3 layer on the surface being the key to its superior oxidation resistance of the HEA at both temperatures.

Graphical Abstract