Uncovering electron scattering mechanisms in NiFeCoCrMn derived concentrated solid solution and high entropy alloys

By Sai Mu, G. Samolyuk, S. Wimmer, M. C. Troparevsky, S. Khan, S. Mankovsky, H. Ebert, G. Malcolm Stocks. npj Computational Materials, 2018

277 citations recorded by the source corpus.

Whilst it has long been known that disorder profoundly affects transport properties, recent measurements on a series of solid solution 3d-transition metal alloys reveal two orders of magnitude variations in the residual resistivity. Using ab initio methods, we demonstrate that, while the carrier density of all alloys is as high as in normal metals, the electron mean-free-path can vary from ~10 Å (strong scattering limit) to ~103 Å (weak scattering limit). Here, we delineate the underlying electron scattering mechanisms responsible for this disparate behavior. While site-diagonal, spin dependent, potential scattering is always dominant, for alloys containing only Fe, Co, and Ni the majority-spin channel experiences negligible disorder scattering, thereby providing a short circuit, while for Cr/Mn containing alloys both spin channels experience strong disorder scattering due to an electron filling effect. Somewhat surprisingly, other scattering mechanisms—including displacement, or size effect, scattering which has been shown to strongly correlate with such diverse properties as yield strength—are found to be relatively weak in most cases.Disordered alloys: Resistivity by smearingSmearing of Fermi surfaces caused by specific alloying elements in high-entropy alloys explains disparate resistivity measurements. A team led by George Malcom Stocks at Oak Ridge National Laboratories in Tennessee, USA, used ab initio methods to investigate electron scattering mechanisms behind differences in residual resistivity of the Cantor-Wu family of face-centered cubic disordered alloys. The simulations first reproduced the experimental observation that alloys containing manganese and chromium had high residual resistivities, while all other Cantor-Wu alloys had low residual resistivities. Single-site electron scattering, in combination with scattering caused by magnetism, showed that this was due to manganese and chromium causing smearing of the Fermi surfaces due to their half-filled d-bands. Better understanding of electronic transport in disordered alloys may help elucidate their more exotic properties.

Subfields: Materials Chemistry, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/c149c31ba9e68678cd34c16ae832fcd6f5825438