Abstract

Novel low-cost Fe50−2xMn30Co10Cr10NixCux (x = 0, 5 at%) high-entropy alloys (HEAs) were produced by vacuum melting and then processed by the cyclic closed-die forging (CCDF) process. It was found that both the as-homogenized and CCDF-processed specimens primarily consisted of a single face-centered cubic (FCC) structure, and the severe plastic strain through CCDF did not result in phase transformations. The microstructure of the CCDF-processed Fe50Mn30Co10Cr10 alloy after the sixth pass demonstrated a uniform structure with ultrafine grains measuring 285 nm in size, whereas for the CCDF-processed Fe40Mn30Co10Cr10Ni5Cu5 alloy, the grain size was 135 nm, with a relatively uniform distribution. The CCDF-processed Fe50Mn30Co10Cr10 and especially the Fe40Mn30Co10Cr10Ni5Cu5 alloy exhibited significantly higher microhardness compared to the as-homogenized state, with microhardness values being 2.42 and 2.72 times higher, respectively. Furthermore, the wear test results indicated that the CCDF processing effectively increased the wear resistance of the alloys, which was attributed to the changes in morphology and distribution of as-cast dendrites, along with the grain refinement of the matrix phase during CCDF. The CCDF-processed Fe40Mn30Co10Cr10Ni5Cu5 alloy exhibited the lowest wear rate, i.e., (1.2 ± 0.2) × 10–5 mm3.N−1.m−1, whereas that for the Fe50Mn30Co10Cr10 alloy was (2.4 ± 0.1) × 10–5 mm3.N−1.m−1. Analysis of wear surfaces indicated that the wear mechanisms of the as-homogenized HEAs were adhesive wear and abrasive wear with some delamination, while plastic deformation and adhesive wear were significantly reduced in the CCDF-processed specimens, especially in the Fe40Mn30Co10Cr10Ni5Cu5 alloy. These findings suggest that CCDF has the potential to achieve cost-effective nanostructured HEAs and to implement them in engineering applications.