Processing and characterization of an electrodeposited nanocrystalline Co-Fe-Ni-Zn multi-principal element alloy film

A Co-Fe-Ni-Zn multi-principal element alloy (MPEA) film with the thickness of about 2.5 & mu;m is processed by electrodeposition. The layer has a nanocrystalline microstructure with the grain size of about 12 nm as determined by transmission electron microscopy. The structure of the majority of the film is face-centered cubic (fcc); however, body-centered cubic (bcc) and amorphous phases with small fractions are also detected. The average hardness and elastic modulus of the coating are 9.2 and 197 GPa, respectively, as determined by nano-indentation. The hardness value is superior compared to other fcc MPEA layers processed by different deposition methods. The enhanced hardness can be attributed to the strengthening effect of the very small grain size and the presence of nanocrystalline bcc and amorphous minority phases. This study demonstrates the ability of electrodeposition for producing hard MPEA layers with the desired composition.