4D evaluation of grain shape and fatigue damage of individual grains in polycrystalline alloys by diffraction contrast tomography using ultrabright synchrotron radiation

Shiozawa, Daiki; Nakai, Yoshikazu; Miura, Ryotaro; Masada, Naoya; Matsuda, Sachi; Nakao, Ryota

doi:10.1016/j.ijfatigue.2015.07.014

Cited by 17 publications

(11 citation statements)

References 24 publications

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“…Recently, Shiozawa et al [17] has reported similar observation. They measured the rotation angle spread from individual grains in polycrystalline alloys by diffraction contrast tomography using ultra bright synchrotron radiation both in the monotonic tension test and in fatigue tests.…”

Section: Resultsmentioning

confidence: 61%

“…This is consistent with the experimental observations that the relative intensity of (111) increases as compared to (200) as we approach the crack, suggesting that slip in the 111 plane in Al is associated with lattice rotation. It is also known that the increase in spread of the rotation angle is related to the increase in dislocation density possibly due to slip near the crack [17]. The stress due to crack tip is expected to be low in fatigue, so only primary slip system is activated in individual grain.…”

Section: Resultsmentioning

confidence: 99%

“…In relatively low-stacking fault energy materials, such as Cu and stainless steel [15,16], the redistribution of dislocations leads to cell structures made of dislocation dipoles in the plastic zone. Recently, an attempt has been made to evaluate the dislocation configurations from the rotation angle spread of 1 to 2° within a grain under monotonic and fatigue loading [17] using diffraction contrast tomography (DCT) for commercially pure Fe, and also to map sub-grain rotation in the deformation region using electron back-scattered diffraction (EBSD) imaging in 304 stainless steel around the corner of a Vickers indentation [18]. In addition, X-ray Laue diffraction scanning has been used to study geometrical necessary dislocations in Cu during accumulation of fatigue cycles [19].…”

Section: Introductionmentioning

confidence: 99%

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Fatigue mediated lattice rotation in Al alloys

2017

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A significant lattice rotation in the plastic zone of a fatigue crack at room temperature in highly oriented Al 1100 and Al 7075 alloys has been observed by employing X-ray diffraction (XRD) and transmission electron microscopy (TEM). The intensity of 111 peak gradually increases as compared to the intensity of 200 peak as we approach the crack, suggesting lattice rotation. The texture was seen to change gradually from the cubic, away from the crack, to a more random orientation close to the crack. We ascribe the lattice rotation to the increase in dislocation density in the plastic zone. The estimated average angle of rotation is approximately 11°, which is sufficient to disturb the cube texture close to the crack. In addition, the observed plastic zone, as estimated by the lattice rotation, is order of magnitude higher as compared to the theoretically predicted plastic zone. This is of great importance, as it leads to a new insight of the underlying physics of the deformation process in the plastic zone under cyclic loading.

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Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fatigue mediated lattice rotation in Al alloys

2017

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“…Consequently, the harmonic-structured SUS304L exhibits a lower resistance to fatigue crack growth owing to grain refinement, and the formation of pores is suppressed by MM. In the future, the three-dimensional fatigue crack shape [41][42][43][44][45][46] and the misorientations near the crack initiation site [47][48][49] will be measured for SUS304L with fatigue damage using synchrotron radiation to describe the mechanism of fatigue crack initiation and propagation in greater detail.…”

Section: -7mentioning

confidence: 99%

Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Kikuchi

Nakatsuka

Nakai

et al. 2019

Frattura Ed Integrità Strutturale

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Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and Kdecreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material is higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, Kth, for the harmonicstructured material is lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, are higher at comparable K. These results can be attributed to a reduction in the effective threshold stress intensity range, K eff,th , due to the presence of fine grains in the harmonic structure.

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“…The authors proposed a hybrid technique combined DCT with the microbeam X-ray method, which enables the estimation of dislocation structure of each crystallographic grain in polycrystalline alloys [9]. In the present study, the change of misorientation of each grain in a polycrystalline alloy and metals in fatigue process is identified as a function of resolved shear stress in the slip direction.…”

Section: Introductionmentioning

confidence: 98%

Fatigue Damage Evaluation by Diffraction Contrast Tomography Using Ultra-Bright Synchrotron Radiation

Nakai

Shiozawa

Asakawa

et al. 2018

The 18th International Conference on Experimental Mechanics

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A three-dimensional grain mapping technique for polycrystalline materials, called X-ray diffraction contrast tomography (DCT), was developed at SPring-8, which is the brightest synchrotron radiation facility in Japan. The developed technique was applied to an austenitic stainless steel. The shape and location of grains could be determined by DCT using the apparatus in a beam line of SPring-8. To evaluate the dislocation structure in fatigue, the total misorientation of individual grains was measured by DCT. The average value of the total misorientation over one sample was increased with the number of cycles. In a grain, the change of the total misorientation was largest for the primary slip plane. The maximum change of the total misorientation in fatigue was larger for planes with larger Schmid factor, and the first fatigue crack initiation was occurred in a grain, which had the greatest change of the total misorientation.

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4D evaluation of grain shape and fatigue damage of individual grains in polycrystalline alloys by diffraction contrast tomography using ultrabright synchrotron radiation

Cited by 17 publications

References 24 publications

Fatigue mediated lattice rotation in Al alloys

Fatigue mediated lattice rotation in Al alloys

Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Fatigue Damage Evaluation by Diffraction Contrast Tomography Using Ultra-Bright Synchrotron Radiation

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