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Statistical analysis of dislocation substructure in commercially pure aluminum subjected to static and dynamic high pressure torsion

Harishchandra Lanjewar (UGent) , Soroosh Naghdy (UGent) , Patricia Verleysen (UGent) and Leo Kestens (UGent)
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Abstract
Severe plastic deformation imposed under high hydrostatic pressure introduces a considerable dislocation substructure in metals from the early stages of deformation, ultimately resulting in grain fragmentation. Characterization and quantification of the substructure require methods with a sufficiently high angular and spatial resolution to reveal the local heterogeneities in orientation differences and the length scales of the substructure. However, the statistical relevance of the observations should be assured which requires relatively large fields of view. In present work, the evolution of dislocation substructures during static and dynamic high pressure torsion processing of commercially pure aluminum is examined. Orientation data obtained by electron backscatter diffraction using two different mapping step sizes are utilized to assess the detection of the dislocation substructures and boundaries during the grain fragmentation stage. Accumulation of distortion in the crystal produces an increase in measurement noise at each pixel which is estimated using Kamaya's plots. The storage of dislocations and related angular misfits reduces the peak height of the probability density distribution of misorientation gradients, moves the peak to higher misorientation gradients and widens the distribution. Superposition of double Rayleigh distributions over the combined dislocation boundary data predicts a slightly higher median for the frequency of geometrically necessary boundaries and larger misorientation gradients across these boundaries in dynamically deformed material. In incidental dislocation boundaries, higher misorientation gradients are only observed at lower equivalent strains. Buildup of shear strain leads to the deterioration in the quality of the fitting to a double Rayleigh distribution and is linked to the complex evolution pattern of the dislocation boundaries. Finally, in statically deformed material, anisotropy in the substructure evolution is observed in the shear and radial planes.
Keywords
Static and dynamic high pressure torsion, Commercial purity aluminum, Statistical boundary analysis, Geometrically necessary dislocation density, Electron backscatter diffraction, HARDNESS EVOLUTION, STRAIN-RATE, DEFORMATION, ORIENTATION, BOUNDARIES, RESOLUTION, GRAIN

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MLA
Lanjewar, Harishchandra, et al. “Statistical Analysis of Dislocation Substructure in Commercially Pure Aluminum Subjected to Static and Dynamic High Pressure Torsion.” MATERIALS CHARACTERIZATION, vol. 160, 2020, doi:10.1016/j.matchar.2019.110088.
APA
Lanjewar, H., Naghdy, S., Verleysen, P., & Kestens, L. (2020). Statistical analysis of dislocation substructure in commercially pure aluminum subjected to static and dynamic high pressure torsion. MATERIALS CHARACTERIZATION, 160. https://doi.org/10.1016/j.matchar.2019.110088
Chicago author-date
Lanjewar, Harishchandra, Soroosh Naghdy, Patricia Verleysen, and Leo Kestens. 2020. “Statistical Analysis of Dislocation Substructure in Commercially Pure Aluminum Subjected to Static and Dynamic High Pressure Torsion.” MATERIALS CHARACTERIZATION 160. https://doi.org/10.1016/j.matchar.2019.110088.
Chicago author-date (all authors)
Lanjewar, Harishchandra, Soroosh Naghdy, Patricia Verleysen, and Leo Kestens. 2020. “Statistical Analysis of Dislocation Substructure in Commercially Pure Aluminum Subjected to Static and Dynamic High Pressure Torsion.” MATERIALS CHARACTERIZATION 160. doi:10.1016/j.matchar.2019.110088.
Vancouver
1.
Lanjewar H, Naghdy S, Verleysen P, Kestens L. Statistical analysis of dislocation substructure in commercially pure aluminum subjected to static and dynamic high pressure torsion. MATERIALS CHARACTERIZATION. 2020;160.
IEEE
[1]
H. Lanjewar, S. Naghdy, P. Verleysen, and L. Kestens, “Statistical analysis of dislocation substructure in commercially pure aluminum subjected to static and dynamic high pressure torsion,” MATERIALS CHARACTERIZATION, vol. 160, 2020.
@article{8641055,
  abstract     = {Severe plastic deformation imposed under high hydrostatic pressure introduces a considerable dislocation substructure in metals from the early stages of deformation, ultimately resulting in grain fragmentation. Characterization and quantification of the substructure require methods with a sufficiently high angular and spatial resolution to reveal the local heterogeneities in orientation differences and the length scales of the substructure. However, the statistical relevance of the observations should be assured which requires relatively large fields of view. In present work, the evolution of dislocation substructures during static and dynamic high pressure torsion processing of commercially pure aluminum is examined. Orientation data obtained by electron backscatter diffraction using two different mapping step sizes are utilized to assess the detection of the dislocation substructures and boundaries during the grain fragmentation stage.

Accumulation of distortion in the crystal produces an increase in measurement noise at each pixel which is estimated using Kamaya's plots. The storage of dislocations and related angular misfits reduces the peak height of the probability density distribution of misorientation gradients, moves the peak to higher misorientation gradients and widens the distribution. Superposition of double Rayleigh distributions over the combined dislocation boundary data predicts a slightly higher median for the frequency of geometrically necessary boundaries and larger misorientation gradients across these boundaries in dynamically deformed material. In incidental dislocation boundaries, higher misorientation gradients are only observed at lower equivalent strains. Buildup of shear strain leads to the deterioration in the quality of the fitting to a double Rayleigh distribution and is linked to the complex evolution pattern of the dislocation boundaries. Finally, in statically deformed material, anisotropy in the substructure evolution is observed in the shear and radial planes.},
  articleno    = {110088},
  author       = {Lanjewar, Harishchandra and Naghdy, Soroosh and Verleysen, Patricia and Kestens, Leo},
  issn         = {1044-5803},
  journal      = {MATERIALS CHARACTERIZATION},
  keywords     = {Static and dynamic high pressure torsion,Commercial purity aluminum,Statistical boundary analysis,Geometrically necessary dislocation density,Electron backscatter diffraction,HARDNESS EVOLUTION,STRAIN-RATE,DEFORMATION,ORIENTATION,BOUNDARIES,RESOLUTION,GRAIN},
  language     = {eng},
  pages        = {11},
  title        = {Statistical analysis of dislocation substructure in commercially pure aluminum subjected to static and dynamic high pressure torsion},
  url          = {http://dx.doi.org/10.1016/j.matchar.2019.110088},
  volume       = {160},
  year         = {2020},
}

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