Diffraction elastic constants of a cubic polycrystal

Wit, R. de

doi:10.1107/s0021889896012812

Cited by 59 publications

(31 citation statements)

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“…The second approach has been developed as a tool for residual stress determination in deformed specimens after the external load is released. The macroscopic stress components are not known in this case; it is thus necessary to define a mesoscopic average stress field depending on the grain orientations, known as the stress orientation distribution function [25][26][27][28] . In this case, the proportionality factors between the strain and stress components are fully determined by the single-crystal elastic constants, although additional restrictive conditions or grain interaction models are often needed to obtain physically consistent solutions for the stress field.…”

Section: Resultsmentioning

confidence: 99%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersionstrengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-ofthe-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from lowtemperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

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Section: Resultsmentioning

confidence: 99%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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“…where a hkl,r is the lattice parameter containing stress effects (from Figure 3), and S1 hkl is the hkl-dependent X-ray elastic constant, determined by the same approximation discussed previously [9] and listed in Table II. The biaxial stress-corrected lattice parameters are shown in the lower part of Figure 5.…”

Section: Resultsmentioning

confidence: 99%

“…The value of S2 420 was calculated to be 0.01374 GPa À1 using the approximation of DeWit [9] and the elastic constants for a Fe-18 wt pct Cr-12 wt pct Ni alloy reported by Bradfield [12] (c 11 = 215.9 GPa, c 12 = 144.6 GPa, and c 44 = 128.9 GPa). In Figure 4, for all four specimens, the a 420 results for w ‡ 30 deg fit well (Pearson correlation coefficient R > 0.993) to a straight line, but the results for w = 0 deg deviate from the fits.…”

Section: Resultsmentioning

confidence: 99%

“…We have investigated, in detail, the interplanar spacings and residual stresses of low-temperature carburized austenitic stainless steels using XRD. Using an analysis based on the most recent approximation for the X-ray elastic constants, [9] we find that the Poisson effect can explain the majority of the apparent XRD lattice parameter variations.…”

Section: Introductionmentioning

confidence: 99%

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Poisson Effects on X-Ray Diffraction Patterns in Low-Temperature-Carburized Austenitic Stainless Steel

Kahn

Michal

Ernst

et al. 2009

Metall Mater Trans A

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Austenitic stainless steel was carburized at low temperature to generate a hard surface layer. X-ray diffractometry (XRD) revealed that this ''case'' contained an expanded fcc lattice and significant residual stresses due to the interstitial carbon. The XRD patterns also exhibit consistent variations with crystallographic orientation. Using published elastic constants for austenitic stainless steel and appropriate approximations for the XRD elastic constants, the XRD peak position variations can be accounted for by orientation-dependent Poisson effects due to biaxial residual stresses. The XRD patterns of specimens containing either compressive or tensile residual stresses were consistent with this hypothesis.

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“…In addition, the average stress and strain in each grain equals those of the surrounding homogeneous matrix. From the elastic stiffness, C ij , of a single crystal of pure Ni, the X-ray elastic constants were estimated using the Kröner model, which was extended by Wit [7]. The elastic stiffnesses of the single crystal used [8] are C 11 ¼ 250.8 GPa, C 12 ¼ 150.0 GPa, and C 44 ¼ 123.5 GPa.…”

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confidence: 99%

Long-Term Stability of Residual Stress Improvement by Water Jet Peening Considering Working Processes

Hashimoto¹,

Osawa²,

Itoh³

et al. 2013

Journal of Pressure Vessel Technology

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To prevent primary water stress corrosion cracking (PWSCC), water jet peening (WJP) has been used on the welds of Ni-based alloys in pressurized water reactors (PWRs). Before WJP, the welds are machined and buffed in order to conduct a penetrant test (PT) to verify the weld qualities to access, and microstructure evolution takes place in the target area due to the severe plastic deformation. The compressive residual stresses induced by WJP might be unstable under elevated temperatures because of the high dislocation density in the compressive stress layer. Therefore, the stability of the compressive residual stresses caused by WJP was investigated during long-term operation by considering the microstructure evolution due to the working processes. The following conclusions were made: The compressive residual stresses were slightly relaxed in the surface layers of the thermally aged specimens. There were no differences in the magnitude of the relaxation based on temperature or time. The compressive residual stresses induced by WJP were confirmed to remain stable under elevated temperatures. The stress relaxation at the surface followed the Johnson-Mehl equation, which states that stress relaxation can occur due to the recovery of severe plastic strain, since the estimated activation energy agrees very well with the self-diffusion energy for Ni. By utilizing the additivity rule, it was indicated that stress relaxation due to recovery is completed during the startup process. It was proposed that the long-term stability of WJP under elevated temperatures must be assessed based on compressive stresses with respect to the yield stress. Thermal elastic-plastic creep analysis was performed to predict the effect of creep strain. After 100 yr of simulated continuous operation at 80% capacity, there was little change in the WJP compressive stresses under an actual operating temperature of 623 K. Therefore, the long-term stability of WJP during actual operation was analytically predicted.

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Diffraction elastic constants of a cubic polycrystal

Cited by 59 publications

References 0 publications

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Poisson Effects on X-Ray Diffraction Patterns in Low-Temperature-Carburized Austenitic Stainless Steel

Long-Term Stability of Residual Stress Improvement by Water Jet Peening Considering Working Processes

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