Abstract
In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of HEAFs were systematically investigated. For Nb-free film (0 at.% Nb), the face-centered cubic (FCC) peaks were identified in the X-ray diffraction (XRD) pattern. The addition of Nb resulted in a broadening of diffraction peaks, a decrease in peak intensity, and the vanishment of high-angle peaks. Transmission electron microscope (TEM) images indicated the formation of nanotwins at low Nb concentrations, and a transition from a single phase FCC solid solution to an amorphous phase was observed with the increasing Nb concentration. The films were strengthened with an increase in Nb concentration. Specifically, the hardness characterized by nanoindentation increased from 6.5 to 8.1 GPa. The compressive yield strength and fracture strength measured from micropillar compression tests were improved from 1.08 GPs and 2.56 GPa to 2.70 GPa and 5.76 GPa, respectively, whereas the fracture strain decreased from >29.4% (no fracture) to 15.8%. Additionally, shear banding was observed in the presence of amorphous phase.
Highlights
Since high entropy alloys (HEAs) were first reported by Yeh et al [1] and Cantor et al [2]in 2004, a great deal of research has been designed to investigate their attractive and versatile properties such as excellent strength and ductility [1,3,4], superior cryogenic fracture toughness [5,6], enhanced corrosion resistance [7,8], high wear resistance [9,10], good irradiation resistance [11], and thermal stability [12], etc
Nbx -CoCrFeMnNi High entropy alloy films (HEAFs) were deposited on 0.55 mm thick (111)-oriented silicon substrates by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets
The Nbx -CoCrFeMnNi HEAFs were successfully prepared by magnetron co-sputtering
Summary
In 2004, a great deal of research has been designed to investigate their attractive and versatile properties such as excellent strength and ductility [1,3,4], superior cryogenic fracture toughness [5,6], enhanced corrosion resistance [7,8], high wear resistance [9,10], good irradiation resistance [11], and thermal stability [12], etc. The equiatomic CoCrFeMnNi. HEA (i.e., Cantor alloy [2]), one of the most studied HEAs, crystallizes as a single phase FCC solid solution. HEA (i.e., Cantor alloy [2]), one of the most studied HEAs, crystallizes as a single phase FCC solid solution It possesses high ductility and strength at cryogenic temperatures but shows a limited strength at room temperature [5,13]. The enhancement in strength is of paramount importance in order to use CoCrFeMnNi HEAs in industry applications
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