Investigation of the electrochemical behavior of AlCoCrFeNi–ZrO2 high entropy alloy composites prepared with mechanical alloying and spark plasma sintering

Abstract

High entropy alloys (HEAs), especially AlCoCrFeNi have received much attention in recent years due to their unique properties. In this regard, the investigation of the various properties of this alloy has been the subject of recent fundamental research. In this study, the electrochemical behavior of Zirconia reinforced AlCoCrFeNi alloy has been investigated. To this end, the Open Circuit Potential (OCP) and Tafel tests were carried out on the samples of AlCoCrFeNi -x%wt. ZrO 2 (x = 0, 5, 10) composites in the 3.5% wt. NaCl solution. The SEM images were taken from the corrosion products during tests. Then, to investigate the effect of time on the type and rate of corrosion, the samples were soaked in the mentioned solution for 24, 48, and 72 h, and then an impedance test was carried out. The results of the Tafel test and SEM images illustrated that the addition of zirconia up to 5%wt. and 10% wt. to the mentioned alloy caused corrosion resistance decrease, and increase, respectively. Increasing the FCC in AlCoCrFeNi − 5%wt. ZrO 2 due to the addition of reinforcement particles decreased the corrosion resistance. The improvement of the corrosion resistance at 10% wt. of zirconia can be attributed to the increase in the ceramic phase with a high electric resistance as well as consistency between passive layers. Electrochemical Impedance Spectroscopy (EIS) in Open Circuit Potential (OCP) indicated that the zirconia addition to the AlCoCrFeNi system delays the formation of passive layers for up to 72 hours; because it leads to creating a rough surface.