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<p>Enhancing the corrosion resistance of Mg-Li alloys represents a critical pathway to broaden the applications of these ultra-light structural materials. The microstructure and corrosion behavior of Mg-5Li-4Sn-2Al-1Zn (LTAZ5421) and Mg-5Li-3Sn-2Al-1Zn (LTAZ5321) alloys in homogeneous and extruded conditions were investigated. Microstructure analysis shows that hot extrusion smooths out the grains through dynamic recrystallization, while the secondary phase breaks up as the Sn content rises. Immersion and electrochemical tests show that corrosion rates generally rise with prolonged exposure, with the extruded LTAZ5421 alloy exhibiting the highest corrosion rate of 4.371&#xa0;mm/y. Initial oxide film formation temporarily delays corrosion, but subsequent film breakdown and micro-galvanic coupling between cathodic Mg<sub>2</sub>Sn and anodic α-Mg accelerate degradation. Higher Sn content increases Mg<sub>2</sub>Sn particles, exacerbating localized pitting and reducing short-term resistance to corrosion. The LTAZ5421 alloy that is extruded forms deep pits because it has a lot of secondary phases. These pits create a small anode/large cathode system that speeds up corrosion. In contrast, the homogeneous 3&#xa0;wt.% Sn alloy demonstrates optimal resistance to corrosion due to weaker pitting driving forces. Corrosion mechanisms are dominated by micro-galvanic effects, with Sn content and extrusion processing critically influencing degradation behavior.</p>

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Role of Sn alloying on the microstructure and corrosion behavior of as-extruded Mg-Li-Al-Zn alloys

  • 期刊论文

  • 发表日期：

    2025年8月5日

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  • Qing Dong,
  • Xuancheng He,
  • Yuhang Guo,
  • Ye Cheng,
  • Wenyu Tang,
  • Lei Wang,
  • Shang Xie,
  • Weiguo Yang,
  • Fengjian Shi

摘要

Enhancing the corrosion resistance of Mg-Li alloys represents a critical pathway to broaden the applications of these ultra-light structural materials. The microstructure and corrosion behavior of Mg-5Li-4Sn-2Al-1Zn (LTAZ5421) and Mg-5Li-3Sn-2Al-1Zn (LTAZ5321) alloys in homogeneous and extruded conditions were investigated. Microstructure analysis shows that hot extrusion smooths out the grains through dynamic recrystallization, while the secondary phase breaks up as the Sn content rises. Immersion and electrochemical tests show that corrosion rates generally rise with prolonged exposure, with the extruded LTAZ5421 alloy exhibiting the highest corrosion rate of 4.371 mm/y. Initial oxide film formation temporarily delays corrosion, but subsequent film breakdown and micro-galvanic coupling between cathodic Mg2Sn and anodic α-Mg accelerate degradation. Higher Sn content increases Mg2Sn particles, exacerbating localized pitting and reducing short-term resistance to corrosion. The LTAZ5421 alloy that is extruded forms deep pits because it has a lot of secondary phases. These pits create a small anode/large cathode system that speeds up corrosion. In contrast, the homogeneous 3 wt.% Sn alloy demonstrates optimal resistance to corrosion due to weaker pitting driving forces. Corrosion mechanisms are dominated by micro-galvanic effects, with Sn content and extrusion processing critically influencing degradation behavior.