skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Extra variable in grain boundary description

Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 1; Related Information: CHORUS Timestamp: 2017-06-26 22:08:52; Journal ID: ISSN 2475-9953
American Physical Society
Country of Publication:
United States

Citation Formats

Hickman, J., and Mishin, Y. Extra variable in grain boundary description. United States: N. p., 2017. Web. doi:10.1103/PhysRevMaterials.1.010601.
Hickman, J., & Mishin, Y. Extra variable in grain boundary description. United States. doi:10.1103/PhysRevMaterials.1.010601.
Hickman, J., and Mishin, Y. Mon . "Extra variable in grain boundary description". United States. doi:10.1103/PhysRevMaterials.1.010601.
title = {Extra variable in grain boundary description},
author = {Hickman, J. and Mishin, Y.},
abstractNote = {},
doi = {10.1103/PhysRevMaterials.1.010601},
journal = {Physical Review Materials},
number = 1,
volume = 1,
place = {United States},
year = {Mon Jun 26 00:00:00 EDT 2017},
month = {Mon Jun 26 00:00:00 EDT 2017}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 26, 2018
Publisher's Accepted Manuscript

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

Save / Share:
  • The dependence of the percolative critical current density at low magnetic fields on YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) layer thickness is studied by comparing grain, J{sub c}{sup G}, and grain-boundary, J{sub c}{sup GB}, critical current densities for a series of ex situ processed YBCO films on a RABiTS template. Both critical current densities decrease as a function of thickness and the values of J{sub c}{sup G} and J{sub c}{sup GB} show a clear correlation which suggests the existence of an interaction between Abrikosov-Josephson vortices on the grain boundaries and Abrikosov vortices in the bulk of the grains. This opens themore » possibility to improve J{sub c}{sup GB} by optimizing the pinning capabilities of the grains.« less
  • Uniaxial plastic deformation of polycrystalline Cu with grain sizes in the range of 5-20 nm was studied by using molecular dynamics computer simulations. We developed a quantitative analysis of plasticity by using localized slip vectors to separate the contributions of dislocation activity from grain boundary sliding. We conclude that the competition between these two mechanisms depends on strain rate and grain size, with the dislocation activity increasing with grain size but decreasing with increasing strain rate. For samples with a 5 nm grain size, dislocations contribute {approx_equal}50% of the total plastic strain during steady state deformation at a rate ofmore » 1x10{sup 8} s{sup -1}, but this fraction decreases to 35% at a rate of 1x10{sup 10} s{sup -1}. When the grain size is increased to 20 nm, dislocations account for 90% of the strain, even at 1x10{sup 10} s{sup -1}. During the initial stages of plastic deformation, grain boundary sliding initially decreases with strain owing to strain-induced relaxation processes within the grain boundaries. The grains also rotate a few degrees during straining to 20%; the rate of rotation (per unit strain) slightly decreases with strain rate. Lastly, we computed the amount of forced atomic mixing during plastic deformation. The mean square separation distance between atom pairs within grain interiors increases with strain at a rate proportional to their distance apart (i.e., the mixing is superdiffusive), but for pair separations greater than the grain size, this rate becomes independent of the separation distance.« less
  • The superconducting grain-boundary (GB) network of coated conductors (CCs) is usually assumed to be a replica of the substrate network. In this letter, we analyze IBAD and RABITS CCs, where such replica either do or do not exist. We have analyzed the effect of GB overgrowth on the critical currents by quantifying the average superconducting grain size and determining the intragrain and grain-boundary critical current densities, J{sub c}{sup G} and J{sub c}{sup GB}. We have employed a recently developed inductive methodology enabling the simultaneous determination of these three parameters. We show that the percolative J{sub c}{sup GB} may be reducedmore » by 50% if the GB networks do not correlate, while J{sub c}{sup G} and the grain pinning properties appear unaffected.« less
  • Grain boundary engineering (GBE) of nickel-based alloy 825 tubes was carried out with different cold drawing deformations by using a draw-bench on a factory production line and subsequent annealing at various temperatures. The microstructure evolution of alloy 825 during thermal-mechanical processing (TMP) was characterized by means of the electron backscatter diffraction (EBSD) technique to study the TMP effects on the grain boundary network and the evolution of grain boundary character distributions during high temperature annealing. The results showed that the proportion of ∑ 3{sup n} coincidence site lattice (CSL) boundaries of alloy 825 tubes could be increased to > 75%more » by the TMP of 5% cold drawing and subsequent annealing at 1050 °C for 10 min. The microstructures of the partially recrystallized samples and the fully recrystallized samples suggested that the proportion of low ∑ CSL grain boundaries depended on the annealing time. The frequency of low ∑ CSL grain boundaries increases rapidly with increasing annealing time associating with the formation of large-size highly-twinned grains-cluster microstructure during recrystallization. However, upon further increasing annealing time, the frequency of low ∑ CSL grain boundaries decreased markedly during grain growth. So it is concluded that grain boundary engineering is achieved through recrystallization rather than grain growth. - Highlights: •The grain boundary engineering (GBE) is applicable to 825 tubes. •GBE is achieved through recrystallization rather than grain growth. •The low ∑ CSL grain boundaries in 825 tubes can be increased to > 75%.« less
  • A constitutive rate equation for grain boundary sliding (GBS), in the presence of grain boundary precipitates, is developed. Langdon`s GBS model is modified by incorporating physically defined back stresses opposing dislocation glide and climb and by modifying the grain size dependence of creep rate. The rate equation accurately predicts the stress dependence of minimum creep rate and change in activation energy occurring as a result of changing the grain boundary precipitate distribution in complex Ni-base superalloys. The rate equation, along with the mathematical formulations for internal stresses, is used to derive a transient creep model, where the transient is regardedmore » as the combination of primary and secondary stages of creep in constant load creep tests. The transient creep model predicts that the transient creep strain is dependent on stress and independent of test temperature. It is predicted that a true steady-state creep will only be observed after an infinitely long time. However, tertiary creep mechanisms are expected to intervene and lead to an acceleration in creep rate long before the onset of a true steady state. The model accurately predicts the strain vs time relationships for transient creep in IN738LC Ni-base superalloy, containing different grain boundary carbide distributions, over a range of temperatures.« less