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<p>Four-point bending fatigue tests were conducted on an AA2024-T351 aluminum alloy plate at <i>R</i> = 0.1, room temperature in humidity of 5, 40, and 90&#xa0;pct RH, respectively. The results demonstrated that, as relative humidity increased from 5 to 40 and 90&#xa0;pct RH, the fatigue limit decreased from 274 to 257&#xa0;MPa (6.2&#xa0;pct in reduction), 240&#xa0;MPa with a total reduction of 12.4&#xa0;pct, indicating that high humidity significantly deteriorated fatigue resistance. The number density of crack initiation sites increased significantly with rising ambient humidity: it measured 0.36&#xa0;mm<sup>−2</sup> at 5&#xa0;pct RH, rose to 0.5&#xa0;mm<sup>−2</sup> at 40&#xa0;pct RH, and further increased to 0.63&#xa0;mm<sup>−2</sup> at 90&#xa0;pct RH. Meanwhile, the strength of these initiation sites showed a gradual decreasing trend. Under dry conditions, cracks primarily originated from pre-fractured Fe-rich particles in the surface layer. In humid environments, the proportion of S-phase (Al<sub>2</sub>CuMg) particles acting as crack initiation sources significantly increased. Analysis indicates that the increase in crack initiation site density with humidity can be attributed to the synergistic effect of water molecules: they not only induce local corrosion damage at the micro-crack tips of pre-fractured Fe-rich particles but also cause the dealloying of S-phase particles, both of which collectively exacerbate crack initiation.</p>

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The Influence of Humidity on the Fatigue Performance of AA2024-T351 Aluminum Alloys

  • 期刊论文

  • 发表日期：

    2026年3月3日

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  • Conghui Xu,
  • Fuqiang Guo,
  • Yihang Li,
  • Huiru Shang,
  • Rongchang Xu,
  • Tongguang Zhai

摘要

Four-point bending fatigue tests were conducted on an AA2024-T351 aluminum alloy plate at R = 0.1, room temperature in humidity of 5, 40, and 90 pct RH, respectively. The results demonstrated that, as relative humidity increased from 5 to 40 and 90 pct RH, the fatigue limit decreased from 274 to 257 MPa (6.2 pct in reduction), 240 MPa with a total reduction of 12.4 pct, indicating that high humidity significantly deteriorated fatigue resistance. The number density of crack initiation sites increased significantly with rising ambient humidity: it measured 0.36 mm−2 at 5 pct RH, rose to 0.5 mm−2 at 40 pct RH, and further increased to 0.63 mm−2 at 90 pct RH. Meanwhile, the strength of these initiation sites showed a gradual decreasing trend. Under dry conditions, cracks primarily originated from pre-fractured Fe-rich particles in the surface layer. In humid environments, the proportion of S-phase (Al2CuMg) particles acting as crack initiation sources significantly increased. Analysis indicates that the increase in crack initiation site density with humidity can be attributed to the synergistic effect of water molecules: they not only induce local corrosion damage at the micro-crack tips of pre-fractured Fe-rich particles but also cause the dealloying of S-phase particles, both of which collectively exacerbate crack initiation.