Separation of static and dynamic displacements in the CrMnFeCoNi high entropy alloy

Abstract

Assessing the local lattice strains in high-entropy alloys (HEAs) is essential if their mechanical properties are to be rationalised and the validity of the highly distorted lattice hypothesis is to be determined. To accomplish this, direct measurements of local distortions need to be made, and the thermal component separated. In this study, variable temperature neutron total scattering measurements were made on the exemplar HEA CrMnFeCoNi, along with pure nickel and an alloy of Ni-37.5Co-25Cr(at.%). A number of methods of determining local atomic displacements from such measurements were used and their efficacy for determining local lattice strains discussed. Using these methods, the local lattice strains have been effectively quantified. The data suggest the HEA does have a comparatively higher strain than the NiCoCr alloy, however, the alloying strains are small in comparison to the thermal component in all cases. As such, whether the local lattice strains are significant and can class the alloy as highly strained remains inconclusive.