Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1905.05156

Kinetics of phase separation, border of miscibility gap in Fe-Cr and limit of Cr solubility in iron at 832 K

Stanisław M. Dubiel·Jan Żukrowski
View original source ↗Read source document ↗Export metadata ↓

Abstract

Kinetics of phase decomposition accompanied by precipitation of sigma-phase in a Fe73.7Cr26.3 alloy isothermally annealed at 832 K was studied by means of Mössbauer spectroscopy. Two stage decomposition process has been revealed by three different quantities viz. the average hyperfine field, , the short-range parameter, alpha1, and the probability of atomic configuration with no Cr atoms within the first two coordination shells around the probe Fe atoms, P(0,0). The first stage, that has terminated after ca.300 h of annealing, has been associated with the decomposition into Fe-rich phase in which the concentration of Cr, determined as 20.9 at.%, can be interpreted as the border of the metastable miscibility gap at 832 K. The second stage can be regarded as a continuation of the phase decomposition process combined with a precipitation of sigma. The three relevant parameters for this stage have also saturation-like behavior vs. annealing time and the saturation can be interpreted as termination of the two processes. The concentration of Cr in the Fe-rich phase has been determined as 19.8 at.% and this value can be regarded as the limit of Cr solubility in iron at 832 K. Both stages of the kinetics were found to be in line with the Johnson-Mehl-Avrami-Kolgomorov equation yielding values of the rate constant and the Avrami exponent. The activation energy of the second-stage process was determined to be by ca.12 kJ/mol higher.

Explore related subjects

cond-mat.mtrl-scicond-mat.str-el

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Stanisław M. Dubiel, Jan Żukrowski. 2019-05-13. Kinetics of phase separation, border of miscibility gap in Fe-Cr and limit of Cr solubility in iron at 832 K. https://doi.org/10.1016/j.matchar.2019.109937

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Incommensurate structural and magnetic modulations in potassium-rich cryptomelane, K$_x$Mn$_8$O$_{16}$ ($x\approx1.45$)

Cryptomelane is a hollandite-like material consisting of K$^+$ cations in an $α$-MnO$_2$ tunnel-like crystallographic motif. Cryptomelane with stoichiometry K$_x$Mn$_8$O$_{16}$ ($x\approx1.45$) has been synthesized and its magnetic properties investigated using variable-temperature magnetic susceptibility, heat capacity, and neutron powder diffraction. Three distinct transitions at $T_1=184$\,K, $T_2=54.5$\,K, and $T_3=24$\,K are observed. At $T_1$ there is a subtle tetragonal$\rightarrow$monoclinic transition associated with emergence of a set of non-magnetic superstructure peaks indexable to a $\vec{k}_\mathrm{struc}\approx0.74\vec{c^*}$ incommensurate modulation parallel to the $α$-MnO$_2$ tunnels. Our findings are consistent with a relation previously reported in titanate hollandites, that $x\approx2|\vec{k}_\mathrm{struc}|$. Magnetic Bragg peaks emerge below $T_2=54.5$\,K, and their positions indicate an incommensurate modulated magnetic structure. The model consistent with the data is a dual-$\vec{k}_\mathrm{mag}$ structure with a ferromagnetic $|\vec{k}_\mathrm{mag}|=0$ component and an incommensurate $\vec{k}_\mathrm{mag}\approx0.37\vec{c^*}$, with the latter most likely to be helical. The period of oscillation of the incommensurate magnetic component is in line with predictions based on a Heisenberg spin Hamiltonian [Mandal \textit{et al}. Phys. Rev. B 90, 104420 (2014)]. Below $T_3=24$\,K, there is a magnetic transition, which gives rise to a different set of magnetic Bragg peaks indicative of a highly complex magnetic structure.

cond-mat.mtrl-sci↗
arXiv2026

An anisotropic functional for two-dimensional material systems

Density function theory is the workhorse of modern electronic structure theory. However, its accuracy in practical calculations is limited by the choice of the exchange-correlation potential. In this respect, two-dimensional materials pose a special challenge, as all these materials and their heterostructures have a crucial similarity. The underlying atomic structures are strongly spatially inhomogeneous, implying that current exchange-correlation functionals, that in almost all cases are isotropic, are ill-prepared for an accurate description. We present an anisotropic screened-exchange potential, that remedies this problem and reproduces the band-gap of 2D materials as well as the piecewise linearity of the total energy with fractional occupation number.

cond-mat.mtrl-sci↗
arXiv2026

Thermally-driven reorientation of the Néel vector in altermagnetic MnTe

Altermagnets are novel magnetic systems that possess a spin-polarized electronic band structure without a net magnetic moment, making them promising for device applications. Hexagonal MnTe, a prototypical altermagnet, arguably exhibits the most properties consistent with theoretical predictions, including an anomalous Hall effect despite a vanishing net magnetization, and altermagnetinduced electronic band splitting. However, fundamental questions remain, including why some effects only appear significantly below the magnetic ordering temperature. Here, we resolve this discrepancy by revealing a reorientation of the Néel vector in single-crystalline MnTe. The Néel vector points 30° from the a-axis at low $T$, before aligning directly with the a-axis around $T\simeq 260$ K. We attribute this to single-ion anisotropy, which depends on temperature-dependent lattice parameters. We obtained these results using muon-spin spectroscopy, magnetization measurements, and X-ray diffraction; we show that the findings are consistent with neutron diffraction. Manipulating this effect, for example through strain, could unlock sensitive electronic detection schemes for external stimuli, paving the way for functional altermagnetic devices.

cond-mat.mtrl-sci↗