Enhanced pitting resistance for high-entropy alloys by precipitating nano-sized L12-strengthened phase

• Published in: Journal of materials science & technology 2025-02, Vol.208, p.53-66
• Main Authors: Li, Tianrun, Wang, Debin, Cui, Jingping, Wang, Qi, Zhang, Suode, Wang, Jianqiang
• Format: Article
• Language: English
• Subjects: High entropy alloys; Passive films; Pitting corrosion; Precipitation
• ISSN: 1005-0302
• DOI: 10.1016/j.jmst.2024.04.051

•A series of precipitation-enhanced HEAs with various L12 contents were designed.•The enrichment of Cr can be achieved in FCC matrix of aged HEAs.•The aged HEAs possessed obvious higher Epit compared to the homogenized HEA.•Aged HEAs achieved the synergy improvement of passive film properties and pitting growth resistance. Precipitation-strengthened HEAs exhibit outstanding integration of strength and toughness at ambient temperature. Nevertheless, precipitates generally reduce the localized corrosion resistance in aggressive solution environments. To solve this problem, a strategy of introducing nano-sized L12 precipitates in CoCrFeNiAlTi HEAs has been proposed in this work. Results demonstrate the pitting corrosion potential can be elevated from 258 mVSCE to 603 mVSCE by increasing the precipitate content to 38 wt.%. Such an improvement in localized corrosion resistance can be attributed to two aspects. Firstly, L12 precipitates tend to be dissolved during the corrosion process, which promotes the heterogeneous nucleation of protective Cr2O3 due to the rapid deposition of oxides/hydroxides of Al/Ti, and improves the passive film stability due to the Cr-rich FCC matrix. Secondly, the dissolution kinetic inside the pits can be suppressed on account of the enrichment of Cr element in the FCC matrix, thus inhibiting the pitting growth. In summary, the current work not only reveals the mechanisms of the nano-sized L12 precipitates upon the corrosion behavior, but also provides a strategy for designing corrosion-resistant HEA. [Display omitted]