A first principles investigation of zinc induced embrittlement at grain boundaries in bcc iron

Hydrogen embrittlement, which severely affects structural materials such as steel, comprises several mechanisms at the atomic level. One of them is hydrogen enhanced decohesion (HEDE), the phenomenon of H accumulation between cleavage planes, where it reduces the interplanar cohesion. Grain boundaries are expected to play a significant role for HEDE, since they act as trapping sites for hydrogen. To elucidate this mechanism, we present the results of first-principles studies of the H effect on the cohesive strength of α-Fe single crystal (001) and (111) cleavage planes, as well as on the Σ5(310)[001] and Σ3(112)[11¯0] symmetrical tilt grain boundaries. The calculated results show that, within the studied range of concentrations, the single crystal cleavage planes are much more sensitive to a change in H concentration than the grain boundaries. Since there are two main types of procedures to perform ab initio tensile tests, different in whether or not to allow the relaxation of atomic positions, which can affect the quantitative and qualitative results, these methods are revisited to determine their effect on the predicted cohesive strength of segregated interfaces.

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An origin of excess vibrational entropies at grain boundaries in Al, Si and MgO: a first-principles analysis with lattice dynamics

Physical Chemistry Chemical Physics ◽

10.1039/d1cp00790d ◽

2021 ◽

Author(s):

T. Yokoi ◽

K. Ikawa ◽

A. Nakamura ◽

K. Matsunaga

Keyword(s):

Bond Length ◽

Grain Boundaries ◽

First Principles ◽

Lattice Dynamics ◽

Excess Entropy ◽

First Principle ◽

Length Changes

Excess vibrational entropies are examined by performing first-principle lattice dynamics for grain boundaries in MgO, Al and Si. Bond-length changes are critical for excess entropy, although their bonding nature is originally very different.

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First Principles Calculations of Defects in Unstable Crystals: Austenitic Iron

MRS Proceedings ◽

10.1557/opl.2011.1383 ◽

2011 ◽

Vol 1363 ◽

Cited By ~ 1

Author(s):

G.J. Ackland ◽

T.P.C. Klaver ◽

D.J. Hepburn

Keyword(s):

Point Defects ◽

First Principles ◽

Defect Formation ◽

Single Layer ◽

Temperature Limit ◽

Reference State ◽

First Principles Calculations ◽

General Picture ◽

Bcc Iron ◽

Defect Energies

ABSTRACTFirst principles calculations have given a new insight into the energies of point defects in many different materials, information which cannot be readily obtained from experiment. Most such calculations are done at zero Kelvin, with the assumption that finite temperature effects on defect energies and barriers are small. In some materials, however, the stable crystal structure of interest is mechanically unstable at 0K. In such cases, alternate approaches are needed. Here we present results of first principles calculations of austenitic iron using the VASP code. We determine an appropriate reference state for collinear magnetism to be the antiferromagnetic (001) double-layer (AFM-d) which is both stable and lower in energy than other possible models for the low temperature limit of paramagnetic fcc iron. Another plausible reference state is the antiferromagnetic (001) single layer (AFM-1). We then consider the energetics of dissolving typical alloying impurities (Ni, Cr) in the materials, and their interaction with point defects typical of the irradiated environment. We show that the calculated defect formation energies have fairly high dependence on the reference state chosen: in some cases this is due to instability of the reference state, a problem which does not seem to apply to AFM-d and AFM-1. Furthermore, there is a correlation between local free volume magnetism and energetics. Despite this, a general picture emerge that point defects in austenitic iron have geometries similar to those in simpler, non-magnetic, thermodynamically stable FCC metals. The defect energies are similar to those in BCC iron. The effect of substitutional Ni and Cr on defect properties is weak, rarely more than tenths of eV, so it is unlikely that small amounts of Ni and Cr will have a significant effect on the radiation damage in austenitic iron at high temperatures.

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First-Principles Study of Substitutional Impurity Segregation in Zirconia, Hafnia, and Yttria-Stabilized-Zirconia Grain Boundaries

2018 Joint Propulsion Conference ◽

10.2514/6.2018-4830 ◽

2018 ◽

Author(s):

Maziar Behtash ◽

Jian Luo ◽

Kesong Yang

Keyword(s):

Grain Boundaries ◽

First Principles ◽

Yttria Stabilized Zirconia ◽

Stabilized Zirconia ◽

Substitutional Impurity ◽

First Principles Study ◽

Impurity Segregation

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First-principles-based mesoscale modeling of the solute-induced stabilization of 〈100〉 tilt grain boundaries in an Al–Pb alloy

Acta Materialia ◽

10.1016/j.actamat.2011.07.056 ◽

2011 ◽

Vol 59 (18) ◽

pp. 7022-7028 ◽

Cited By ~ 7

Author(s):

Y. Purohit ◽

L. Sun ◽

O. Shenderova ◽

R.O. Scattergood ◽

D.W. Brenner

Keyword(s):

Grain Boundaries ◽

First Principles ◽

Mesoscale Modeling

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Environment Sensitive Embedding Energies of Impurities, and Grain Boundary Relaxation in Iron

MRS Proceedings ◽

10.1557/proc-238-481 ◽

1991 ◽

Vol 238 ◽

Cited By ~ 1

Author(s):

Genrich L. Krasko

Keyword(s):

Charge Density ◽

First Principles ◽

Electron Charge ◽

Deformation Wave ◽

Electron Charge Density ◽

Impurity Site ◽

Embedded Atom ◽

Bcc Iron ◽

Boundary Relaxation ◽

Low Solubility

ABSTRACTImpurities, such as H, P, S, B, etc, have a very low solubility in iron, and therefore prefer to segregate at the grain boundaries (GBs). In order to analyze the energetics of the impurities on the iron GB, the LMTO calculations were performed on a simple 8-atom supercel 1 emulating a typical (capped trigonal prism) GB environment. The so-called “environment-sensitive embedding energies” were calculated for H, B, C, N, O, Al, Si, P, and S, as a function of the electron charge density due to the host atoms at the impurity site. It was shown that, at the electron charge density typical of a GB, B and C have the lowest energy among the analyzed impurities, and thus would compete with them for the site on the GB, tending to push the other impurities off the GB. The above energies were then used in a modified Finnis-Sinclair embedded atom approach for calculating the equilibrium interplanar distances in the vicinity of a (111) σ3 tilt GB plane, both for the clean GB and that with an impurity. These distances were found to be oscillating, returning to the equilibrium spacing between (111) planes in bulk BCC iron by the 10th-12th plane off the GB plane. H, B, C, N and O actually dampen the deformation wave (making the oscillation amplitudes less than in the clean GB), while, Al, Si, P and S result in an increase of the oscillations. The effect of B, C, N and O may be interpreted as cohesion enhancement; this conclusion supports our earlier first-principles results [1] on B and C.

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Fast and scalable prediction of local energy at grain boundaries: machine-learning based modeling of first-principles calculations

Modelling and Simulation in Materials Science and Engineering ◽

10.1088/1361-651x/aa8276 ◽

2017 ◽

Vol 25 (7) ◽

pp. 075003 ◽

Cited By ~ 12

Author(s):

Tomoyuki Tamura ◽

Masayuki Karasuyama ◽

Ryo Kobayashi ◽

Ryuichi Arakawa ◽

Yoshinori Shiihara ◽

...

Keyword(s):

Machine Learning ◽

Grain Boundaries ◽

First Principles ◽

Local Energy ◽

First Principles Calculations

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Anomalous diffusion of water molecules at grain boundaries in ice Ih

Physical Chemistry Chemical Physics ◽

10.1039/c8cp00933c ◽

2018 ◽

Vol 20 (20) ◽

pp. 13944-13951 ◽

Cited By ~ 6

Author(s):

Pedro Augusto Franco Pinheiro Moreira ◽

Roberto Gomes de Aguiar Veiga ◽

Ingrid de Almeida Ribeiro ◽

Rodrigo Freitas ◽

Julian Helfferich ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Grain Boundaries ◽

Anomalous Diffusion ◽

First Principles ◽

Water Molecules ◽

Diffusive Behavior ◽

Classical Molecular Dynamics ◽

Dynamics Simulations

First-principles and classical molecular dynamics simulations show that diffusion of water molecules at pre-melted grain boundaries in ice is glassy-like, showing sub-diffusive behavior.

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