Improvement of corrosion resistance and magnetic properties of FeCoNiAl_0.2Si_0.2 high entropy alloy via rapid-solidification

In this work, a rapid-solidification method was utilized on FeCoNiAl_0.2Si_0.2 high entropy alloy (HEA) and its effects on microstructure, corrosion resistance and magnetic properties were systematically investigated. Rapid-solidified and slowly-cooled FeCoNiAl_0.2Si_0.2 specimens were produced by melt-spinning and induction melting, respectively. It was found that, slowly-cooled FeCoNiAl_0.2Si_0.2 exhibits dendrite structure with compositional segregation of Al, Si and Ni, as well as the precipitation of L1₂-type ordered phase in the solid solution matrix, while rapid-solidification effectively promotes the structural and compositional homogeneity. Moreover, rapid-solidification leads to significant enhancement in the stability of the passive film, and thus results in remarkable increase in corrosion resistance compared to its slowly-cooled counterpart. Besides, the distribution of constituent elements plays an important role in the formation of passive film on the surface of this HEA. In addition, the H_c of the rapid-solidified specimen exhibits only nearly 1/5 of its slowly-cooled counterpart, indicating significant positive effect of rapid-solidification on soft magnetic properties of FeCoNiAl_0.2Si_0.2. This work provides a novel route for further development of HEAs with excellent corrosion resistance and soft magnetism.