Microstructural evolution, electrochemical and corrosion properties of Al x CoCrFeNiTi y high entropy alloys

Y. Qiu*, S. Thomas, D. Fabijanic, A. J. Barlow, H. L. Fraser, N. Birbilis

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    196 Citations (Scopus)

    Abstract

    The microstructure of the Al x CoCrFeNiTi y high entropy alloy (HEA) system was studied using X-ray diffraction, scanning and transmission electron microscopy. A microstructural evolution from single-phase FCC to FCC + BCC + B2 occurred with increasing Al content. The addition of a comparatively small amount of Ti led to the formation of a Fe-Cr sigma phase. The corrosion characteristics of the alloy system were studied across different compositions, with such an alloy system exhibiting a high resistance to general corrosion, superior to stainless steel 304L in 0.6 M NaCl. Cyclic potentiodynamic polarisation suggested that the HEAs studied underwent pitting corrosion following breakdown. From exposure testing, it was seen that very fine pitting, although not extensive in nature, was the principle form of corrosion for Al x CoCrFeNiTi y after prolonged immersion. There was little evidence of microgalvanic corrosion or selective dissolution of a particular phase observed, despite the heterogeneous microstructure and significant elemental segregation in the alloys studied. The composition of the surface films formed upon the Al x CoCrFeNiTi y alloys were elaborated by X-ray photoelectron spectroscopy, which provided new and further insights regarding the surface films of such alloys. The study herein contributes to an emerging understanding of the corrosion characteristics of high entropy alloys.

    Original languageEnglish
    Article number107698
    JournalMaterials and Design
    Volume170
    DOIs
    Publication statusPublished - 15 May 2019

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