Role of Co content on the microstructure and anti-corrosion performance of high-hardness AlNiYCox high entropy metallic glasses

Abstract

In the present paper, the role of Co content on phase structure, thermal stability and anti-corrosion performance of melt-spun (Al1/3Ni1/3Y1/3)100-xCox (x= 5, 8, 12, 15 and 20 at.%) high entropy metallic glasses has been investigated. The microstructure and average hardness of AlNiYCox alloy ribbons were characterized and detected using a scanning electron microscope (SEM) and Vickers-type hardness tester, respectively. The corrosion behavior in 3.5 wt% NaCl solution was tested through the conventional potentiodynamic polarization curves (Tafel curves) and electrochemical impedance spectroscopy (EIS). Results suggested that all kinds of high entropy metallic glass ribbons could remain amorphous nature and the crystallization onset temperature are all above 750 K. The average hardness value of each ribbon sample is more than 530 HV0.1 as well. With the increase of Co content, the corrosion resistance begins to enhance and then lowers gradually. When the Co content increases from 5 at.% to 20 at.%, it can result in a decrease of corrosion current density from 9.546 µA/cm2 of the (Al1/3Ni1/3Y1/3)95Co5 to 0.508 µA/cm2 of the (Al1/3Ni1/3Y1/3)92Co8 and 0.741 µA/cm2 of the (Al1/3Ni1/3Y1/3)80Co20 alloy ribbons. Therefore, it is assumed that adding appropriate content of Co element into (Al1/3Ni1/3Y1/3)100-xCox alloys can enhance ability to resist corrosion in 3.5 wt% NaCl solution. The ribbons with 8 at.% Co exhibited the excellent anti-corrosion performance in this current study.