Abstract:Since the landmark development of the Scherrer Method a century ago, multiple generations of width methods for X-ray diffraction originated to non-invasively and rapidly characterize the property-controlling sizes of nanomaterials.
“…The peak shift was due to the average pressure of ~ 83 GPa in the analyzed section, and the peak broadening was largely due to the densities (volume fractions) and distributions of dislocations and twins (as tabulated in Table S1 ). Researchers have often attempted to decouple the effects of the various broadening sources for 1D XRD line profiles, but no solution has been universally accepted 35 , 36 . Figure 2 The pressure distribution and microstructure for select time steps of shocked Ta.…”
Section: Resultsmentioning
confidence: 99%
“…While high-speed diffraction can theoretically track nanoscale deformations in real-time, the traditional methods for interpreting diffractograms are unfortunately lacking 32 , 33 . For example, numerous methods for characterizing defects from the widths of diffractogram peaks often yield conflicting results 34 – 36 . To resolve such uncertainties, researchers have recently generated virtual diffractograms from atomistic simulations 36 – 38 .…”
Section: Introductionmentioning
confidence: 99%
“…For example, numerous methods for characterizing defects from the widths of diffractogram peaks often yield conflicting results 34 – 36 . To resolve such uncertainties, researchers have recently generated virtual diffractograms from atomistic simulations 36 – 38 . By comparing the ground truths of the atomistic simulations to interpretations of the corresponding virtual diffractograms, they evaluated the efficacies of the interpretative methods themselves.…”
During the various stages of shock loading, many transient modes of deformation can activate and deactivate to affect the final state of a material. In order to fundamentally understand and optimize a shock response, researchers seek the ability to probe these modes in real-time and measure the microstructural evolutions with nanoscale resolution. Neither post-mortem analysis on recovered samples nor continuum-based methods during shock testing meet both requirements. High-speed diffraction offers a solution, but the interpretation of diffractograms suffers numerous debates and uncertainties. By atomistically simulating the shock, X-ray diffraction, and electron diffraction of three representative BCC and FCC metallic systems, we systematically isolated the characteristic fingerprints of salient deformation modes, such as dislocation slip (stacking faults), deformation twinning, and phase transformation as observed in experimental diffractograms. This study demonstrates how to use simulated diffractograms to connect the contributions from concurrent deformation modes to the evolutions of both 1D line profiles and 2D patterns for diffractograms from single crystals. Harnessing these fingerprints alongside information on local pressures and plasticity contributions facilitate the interpretation of shock experiments with cutting-edge resolution in both space and time.
“…The peak shift was due to the average pressure of ~ 83 GPa in the analyzed section, and the peak broadening was largely due to the densities (volume fractions) and distributions of dislocations and twins (as tabulated in Table S1 ). Researchers have often attempted to decouple the effects of the various broadening sources for 1D XRD line profiles, but no solution has been universally accepted 35 , 36 . Figure 2 The pressure distribution and microstructure for select time steps of shocked Ta.…”
Section: Resultsmentioning
confidence: 99%
“…While high-speed diffraction can theoretically track nanoscale deformations in real-time, the traditional methods for interpreting diffractograms are unfortunately lacking 32 , 33 . For example, numerous methods for characterizing defects from the widths of diffractogram peaks often yield conflicting results 34 – 36 . To resolve such uncertainties, researchers have recently generated virtual diffractograms from atomistic simulations 36 – 38 .…”
Section: Introductionmentioning
confidence: 99%
“…For example, numerous methods for characterizing defects from the widths of diffractogram peaks often yield conflicting results 34 – 36 . To resolve such uncertainties, researchers have recently generated virtual diffractograms from atomistic simulations 36 – 38 . By comparing the ground truths of the atomistic simulations to interpretations of the corresponding virtual diffractograms, they evaluated the efficacies of the interpretative methods themselves.…”
During the various stages of shock loading, many transient modes of deformation can activate and deactivate to affect the final state of a material. In order to fundamentally understand and optimize a shock response, researchers seek the ability to probe these modes in real-time and measure the microstructural evolutions with nanoscale resolution. Neither post-mortem analysis on recovered samples nor continuum-based methods during shock testing meet both requirements. High-speed diffraction offers a solution, but the interpretation of diffractograms suffers numerous debates and uncertainties. By atomistically simulating the shock, X-ray diffraction, and electron diffraction of three representative BCC and FCC metallic systems, we systematically isolated the characteristic fingerprints of salient deformation modes, such as dislocation slip (stacking faults), deformation twinning, and phase transformation as observed in experimental diffractograms. This study demonstrates how to use simulated diffractograms to connect the contributions from concurrent deformation modes to the evolutions of both 1D line profiles and 2D patterns for diffractograms from single crystals. Harnessing these fingerprints alongside information on local pressures and plasticity contributions facilitate the interpretation of shock experiments with cutting-edge resolution in both space and time.
“…11,13,[17][18][19][20] To address these issues, researchers have focused on several hierarchical modifications to nanostructured alloys, including heterogeneous gradient/bimodal grain structures, [21][22][23] heterogeneous grain-boundary (GB) chemistry/structure, 24 and nanotwinned (NT) materials. [25][26][27][28][29] In parallel, the development of several unique in situ nano-and micromechanical testing techniques 16,[30][31][32] have allowed for a more detailed understanding of fatigue and fracture behavior of nanocrystalline and nanotwinned metals and alloys.…”
Metals and alloys with nanoscale structural features (such as grain size or twin thickness <100 nm) exhibit exceptional strength and unusual deformation mechanisms. But, the suppressed dislocation slip, grain-boundary instability, and limited strain hardening in these nanostructured metals can be detrimental to fatigue and fracture properties. In this article, recent advances in understanding the structural origins of fatigue and fracture resistance of nanocrystalline and nanotwinned metals and alloys are reviewed. Based on this understanding, microstructural engineering strategies, such as gradient grain size, controlled boundary mobility, or hierarchical nanotwins, alter the deformation modes and provide promising paths to develop nanostructured materials with improved fatigue and fracture properties.
“…For example, the mean crystallite size can be evaluated by either the Scherrer equation application to a single peak or from Rietveld refinement that fits all the peaks of the pattern and apply the full width at half maximum (FWHM -Scherrer equation) or Voigt Integral Breadth (LVolIB). [23,35,36].…”
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