Outstanding performance of FeNiCoCr-based high entropy alloys: the role of grain orientation and microsegregation

Abstract

High entropy alloys have presented more interests in energy related applications including catalyst materials. However, the engineering application of these materials is still hindered by lacking information of their mechanical and electrochemical behaviors. Different high-entropy alloys based on FeNiCoCr system (FeNiCoCr, FeNiCoCrCu, and FeNiCoCrMn) were fabricated based on thermodynamic predictions and studied in terms of microstructure and grain orientation in relationship with their mechanical and catalytic properties. The single-phase FCC solid-solutions were obtained in all the fabricated alloys, which have shown excellent ductility during compressive testing. The coarse dendrictic microstructure was observed in FeNiCoCr and FeNiCoCrMn alloys, while the finer one was obtained in FeNiCoCrCu, which presented higher value of microhardness. Analyses of EBSD measurements in the studied alloys have shown a strong relationship between the grain orientations and their mechanical behavior. Furthermore, a good corrosion resistance was achieved for the three fabricated alloys, being better the alloy with the addition of Cu element. Among the studied alloys, FeNiCoCrCu has presented excellent electrocatalytic activity and stability toward hydrogen evolution reaction in acidic media. The enhancement in corrosion resistance of FeNiCoCrCu could be associated with presence of {111}//ND component, while its strong catalytic activity is related to the {220}//ND orientation dominated by the material. This outstanding performance of FeNiCoCrCu has demonstrated as a promising candidate to substitute Pt for application as electrocatalyst in acidic media.