스파크 플라즈마 소결된 FeCrMnNiCo 고엔트로피 합금의 0.01 M HCl 수용액에서의 부식 거동에 밀링 시간이 미치는 영향

The effect of ball milling time on the microstructure and corrosion behavior of the high-entropy FeCrMnNiCo alloy was investigated in a 0.01 M HCl aqueous solution. Alloy powders were prepared by varying the milling durations for 6, 12, 24, and 48 h, followed by spark plasma sintering at 1,000 °C and 80 MPa. X-ray diffraction analysis of the sintered specimens confirmed the presence of both FCC and Cr₂₃C₆ in all samples, with negligible phase variation observed as a function of milling time. SEM-EDS analysis revealed that increasing the milling time led to a reduction in the size and Cr concentration of the Cr-rich secondary phases. Conversely, the Cr content within the alloy matrix exhibited a corresponding increase. Potentiodynamic polarization tests demonstrated that both the corrosion potential and pitting potential increased with longer milling times. Pitting corrosion was generally observed to initiate at the phase boundaries between the Cr-rich secondary phase and the matrix. The 6 h specimen exhibited the lowest resistance to pitting, which was attributed to the significant Cr concentration gradient between the Cr-rich phase and the matrix, inducing a local galvanic effect. Consequently, these findings suggest that the FeCrMnNiCo alloy can attain a stable microstructure and superior corrosion resistance when subjected to milling for 12 h or longer.