Stabilization of the hcp structure in the ruthenium-substituted high-entropy Cantor alloys Cr20Mn20(Fe20−xRux)Co20Ni20(0≤ x≤20) and their magnetic and structural properties

OpenAlex İngilizce

While the valence electron concentration (VEC) of the system Cr 20 Mn 20 ( Fe 20 − x Ru x ) Co 20 Ni 20 ( 0 ≤ x ≤ 20 ), where Fe is partially substituted by Ru, remains at eight electrons per atom (e/a), the structure undergoes a change from single-phase fcc ( x = 0 ) to a two-phase fcc/hcp system as x increases, with the VEC of both phases remaining at or very close to 8 e/a. The hcp phase forms already at 5 at% Ru substitution. From studies on thermal expansion determined through x-ray diffraction, magnetization, and Mössbauer spectroscopy, we find that the fcc phase is magnetically active and possesses moment-volume instabilities with energetically close-lying low-spin and high-spin states, while the hcp phase is nonmagnetic in accordance with the predictions of theory. The results show that the hcp phase can be stabilized at a volume fraction of up to 80% under ambient conditions in a predominantly 3-d alloy with VEC = 8 e/a.