Insight into microstructure evolution on anti-corrosion property of AlxCoCrFeNiC0.01 high-entropy alloys using scanning vibration electrode technique

The effect of microstructure on the corrosion resistance of AlxCoCrFeNiC0.01 (x = 0.2, 0.7, and 1.2) high-entropy alloys (HEAs) was systematically studied in this work. The microstructure evolution by regulating the Al content was analyzed in detail. Corrosion behavior was in situ monitored using the scanning vibration electrode technique, as well as some traditional electrochemical measurements. It is interesting to find that the compositions of body-centered cubic (bcc) and face-centered cubic (fcc) phases changed with the rising Al content, while the corresponding electrochemical responses for both phases were discriminated using the scanning Kelvin probe force microscopy method. Cr element was mainly distributed in the bcc phase for Al0.2 (x = 0.2) alloy, while its distribution changed to the fcc phase for the Al0.7 and Al1.2 alloys. The micro-galvanic corrosion cells formed between Cr-depleted and Cr-rich phases, resulting in the localized corrosion behaviors for the AlxCoCrFeNiC0.01 HEAs, and the order for anti-corrosion property was Al0.2 > Al1.2 > Al0.7 HEAs.