Regensburg 2022 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 13: Non-equilibrium Phenomena in Materials Induced by Electrical and Magnetic Fields 3

MM 13.6: Vortrag

Dienstag, 6. September 2022, 12:15–12:30, H45

Nanocrystalline CoCrFeNiGax (x = 0.5, 1.0) high entropy alloys: structural and magnetic features — •Natalia Shkodich, Marina Spasova, and Michael Farle — Faculty of Physics and Center of Nanointegration (CENIDE), University of Duisburg-Essen, Duisburg, 47057 Germany

Nanocrystalline single fcc phase CoCrFeNiGax (x = 0.5, 1.0) high entropy alloy (HEA) powder particles with good structural and compositional homogeneity were successfully fabricated by high energy ball milling (HEBM). Characterization by XRD, SEM/EDX, and TEM/EDX shows that the fcc phase with the refined microstructure of nanosized grains (~10 nm) could be obtained after 190 min of HEBM at 900 rpm. We used HEBM powders to fabricate homogeneous nanocrystalline bulk HEAs by spark plasma sintering (SPS). SPS at 1073 K of the CoCrFeNiGa0.5 HEA powder increases the crystallinity of the fcc phase, while for the equiatomic CoCrFeNiGa powder a partial transformation of the fcc into the bcc phase is observed. The nanocrystalline HEA CoCrFeNiGax (x = 0.5, 1.0) powders show a paramagnetic behavior at room temperature and a Curie temperature (Tc) is of 127K-130K. After SPS, the CoCrFeNiGa bulk material is ferromagnetic up to Tc =775K. Its saturation magnetization Ms (300K) increases by a factor of 10 as compared to the HEA powder. The SPS of the CoCrFeNiGa0.5 HEA powder, however, does not change its paramagnetic nature at ambient temperature. This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) within CRC/TRR 270, project S01 (project ID 405553726).