Unveiling the effect of strain path-dependent microstructural evolution on the electrochemical behavior of cold-rolled [FeNi]69Cr15Mn10Nb6 high-entropy alloy

Abstract

In the present work, [FeNi]₆₉Cr₁₅Mn₁₀Nb₆ high-entropy alloys (HEAs) were subjected to a heavy cold-rolling process at ambient temperature through two distinct routes, namely unidirectional cold-rolling (UCR) and multistep cross cold-rolling (MSCCR). This was done to investigate the effect of strain path-dependent microstructural evolution on the electrochemical behavior of the alloys in a 0.5 M H₂SO₄ solution. The as-homogenized specimen displayed a two-phase microstructure with [FeNiNb]-rich dendrites distributed in a nearly homogenous face-centered cubic (FCC) high-entropy alloy matrix. It was found that the [FeNiNb]-rich dendrites elongated, broke down, and elongated along the rolling direction in both processing routes. In the MSCCR-processed specimen, the dendrites exhibited a smaller average size with a more uniform distribution compared to the UCR sample, which was mainly ascribed to the elongation mechanisms in the normal and transverse directions during the MSCCR route. Electrochemical studies demonstrated a decrease in corrosion current density due to high imposed strains in the UCR. Meanwhile, a more positive trend was observed in MSCCR processing. Consequently, achieving uniformly distributed small dendrites and uniform grain refinement through the MSCCR route provided ideal conditions for forming passive layer with superior protection properties.