Antonín Dlouhý

TL;DR: In this article, an equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (fcc) crystal structure, was produced by arc melting and drop casting.

TL;DR: In this article, the authors evaluated the phase stability of CrMnFeCoNi and showed that it is a single-phase solid solution after homogenization for 2 days at 1200°C and remains in this state after a subsequent anneal at 900°C for 500 days.

TL;DR: In this paper, the yield strength of the CrMnFeCoNi high-entropy alloy was determined in compression as a function of grain size and temperature, and the resulting Hall-Petch slopes were straight lines with different slopes that depend on the number of twin boundaries per grain.

TL;DR: In this paper, the authors show how conventional and advanced mechanical, chemical, and microstructural methods can be used to characterize cast single crystal Ni-base superalloy (SX) plates across multiple length scales.

Abstract: We present experimental data showing that the equiatomic CrMnFeCoNi high-entropy alloy undergoes two magnetic transformations at temperatures below 100 K while maintaining its fcc structure down to 3 K. The first transition, paramagnetic to spin glass, was detected at 93 K and the second transition of the ferromagnetic type occurred at 38 K. Field-assisted cooling below 38 K resulted in a systematic vertical shift of the hysteresis curves. Strength and direction of the associated magnetization bias was proportional to the strength and direction of the cooling field and shows a linear dependence with a slope of $0.006\ifmmode\pm\else\textpm\fi{}0.001 \mathrm{emu}\mathrm{T}$. The local magnetic moments of individual atoms in the CrMnFeCoNi quinary fcc random solid solution were investigated by ab initio (electronic density functional theory) calculations. Results of the numerical analysis suggest that, irrespective of the initial configuration of local magnetic moments, the magnetic moments associated with Cr atoms align antiferromagnetically with respect to a cumulative magnetic moment of their first coordination shell. The ab initio calculations further showed that the magnetic moments of Fe and Mn atoms remain strong (between 1.5 and $2\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$), while the local moments of Ni atoms effectively vanish. These results indicate that interactions of Mn- and/or Fe-located moments with the surrounding magnetic structure account for the observed macroscopic magnetization bias.