Microstructure and Corrosion Behavior of CoCr_xCuFeMnNi High‐Entropy Alloys Prepared by Vacuum Hot‐Pressing Sintering

Abstract

Herein, CoCrxCuFeMnNi (x = 0, 0.5, 1.0, 1.5, and 2.0, in molar ratio) high‐entropy alloys (HEAs) are prepared through vacuum hot‐pressing sintering. The influences of Cr content on the microstructure and the corrosion behavior in 3.5% NaCl solution are studied. The alloys are mainly composed of two face‐centered cubic (FCC) phases, namely, Cr–Co–Fe–Mn–Ni (or Co–Fe–Mn–Ni)‐rich FCC1 phase and Cu–Mn–Ni‐rich FCC2 phase. With the increase of Cr content, The FCC1‐phase area expands and the FCC2 phase area shrinks. In 3.5% NaCl solution, the corrosion current density (icorr) and average corrosion rate (Vcorr) of the HEAs decrease with the increase in Cr content. The icorr and Vcorr of Cr2.0 alloy are lower at 1.87 × 10−6A cm−2 and 0.02 mm year−1, respectively. The increase of transfer resistance (Rp) and decrease of relative thickness (CPE1−1) of the passivation film indicate that the more difficult it is for ions in the corrosive medium to pass through the capacitor layer, the better the corrosion resistance of the alloy. Improvement of the corrosion resistance is mainly due to the formation of denser Cr2O3 passivation film and reduction of the segregation degree of Cu in the FCC2 phase.

Corrosion‐Resistant Biomedical High‐Entropy Alloys: A Review

“…The positive effect of Cr element on corrosion resistance is confirmed in another research of CoCr x CuFeMnNi HEAs. [ 68 ]…”

“…The positive effect of Cr element on corrosion resistance is confirmed in another research of CoCr x CuFeMnNi HEAs. [68] However, the detrimental influence of the Cr element on corrosion resistance for FeCoNiCr x HEAs has also been reported. [69] In 0.5 M H 2 SO 4 solutions, there is a distinguished active area in the anodic curves of FeCoNi alloys, which is clearly slight in FeCoNiCr 0.5 and FeCoNiCr HEAs.…”