TDPAC studies on the recovery of Ag plastically deformed at room temperature

Wodniecka, B.; Marszałek, M.; Wodniecki, P.

doi:10.1088/0953-8984/1/41/002

Cited by 6 publications

(5 citation statements)

References 32 publications

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“…Quantities which are derived from the gradient elastic tensor, like the stress dependence of the EFG under isostatic pressure or uniaxial pressure in polycrystalline materials, have been measured with PAC in many hexagonal systems [2,[13][14][15][16] without knowledge of the corresponding gradient elastic constants. However, it is the exact knowledge of these constants which allows to explain aforementioned dependencies and, in addition to it, to gain further information about the studied materials as for instance about intrinsic strains in thin films [12] and quantum dots [17][18][19] or dislocation and point defect densities [3,20,21].…”

Section: Introductionmentioning

confidence: 99%

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Brüsewitz

Vetter

Hofsäss

2015

J. Phys.: Condens. Matter

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We present ab-initio calculations of the independent components of gradient elastic tensors, so-called gradient elastic constants, which relate electric field gradient tensors to stress or strain tensors. The constants of cubic and hexagonal metals, MAX phases, and zinc oxide were determined within the framework of density functional theory by using the augmented plane waves plus local orbitals method implemented in the WIEN2k code. Comparison with experimental gradient elastic constants and electric field gradients' stress dependencies suggest an accuracy of about 30% of the calculated constants, independent of the probe that detects the field gradient being self- or foreign-atom. Changes in the electric field gradient take place by strain-induced asymmetric occupations of the p and d states in the valence region for all investigated materials. Volume and structural dependencies of the electric field gradient can directly be determined from this fundamental approach and are, for hexagonal closed packed metals, consistent with vanishing electric field gradients around ideal close packing and volume dependencies larger than one. The concept of these calculations is applicable in any hyperfine interaction method and, thus, can be used to gain information about intrinsic strains in systems where the experimental gradient elastic constants are inaccessible.

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Section: Introductionmentioning

confidence: 99%

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Brüsewitz

Vetter

Hofsäss

2015

J. Phys.: Condens. Matter

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“…The method is suitable to identify point defects, which are trapped at the probe atom, by their characteristic EFGs [9][10][11]. Randomly distributed defects induce a distribution broadening of the field gradient tensor components by their strain fields, as seen in cubic and hexagonal metals [12,13]. In contrast to the above-mentioned PAC experiments, which have been performed after deformation, in-situ experiments have only been conducted in order to investigate the effect of elastic strains on the EFGs [14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Perturbed angular correlation studies of uniaxial compressive stressed zinc, titanium, rutile, Ti₂AlN, and Nb₂AlC

Brüsewitz¹,

Vetter²,

Hofsäss³

et al. 2014

J. Phys.: Condens. Matter

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We use the perturbed angular correlation method with (111)In-(111)Cd probe atoms to in situ study the changes in the electric field gradient at room temperature of polycrystalline Ti(2)AlN and Nb(2)AlC, titanium and zinc, and rutile samples, as a function of cyclic uniaxial compressive loads. The load dependence of the quadrupole coupling constant νQ was found to be large in titanium and zinc but small in Ti(2)AlN, Nb(2)AlC and rutile. Reversible and irreversible increases in the electric field gradient distribution widths were found under load and after releasing the load, respectively. Annihilation of dislocations, as well as elastic deformation, are considered to contribute to the reversible behavior. The irreversible response must be caused by a permanent increase in dislocation and point defect densities. The deformation induced broadening of the electric field gradient can be recovered by post-annealing of the deformed sample.

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“…[4][5][6][7] The dynamical behavior of point defects in metals is usually characterized by investigating annealing kinetics following extensive cold work. The recovery of induced plastic deformation is monitored using various techniques such as electrical resistivity, [8] positron lifetimes, [9] perturbed-angular correlation, [10] Mossbauer spectroscopy, [11] ultrasonic attenuation, [12] etc. In contrast to these two-step experiments, it is desirable to be able to investigate these kinetics in situ during deformation of materials in a single step.…”

Section: Introductionmentioning

confidence: 99%

In-situ nuclear magnetic resonance investigation of strain, temperature, and strain-rate variations of deformation-induced vacancy concentration in aluminum

Murty

Detemple

Kanert

et al. 1998

Metall Mater Trans A

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Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin-LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. The new CUT-sequence pulse method allowed an accurate evaluation of the strain-enhanced vacancy diffusion and, thus, the excess vacancy concentration during deformation as a function of strain, strain rate, and temperature. Due to skin effect problems in metals at high frequencies, thin foils of Al were used and experimental results correlated with models based on vacancy production through mechanical work (vs thermal jogs), while in situ annealing of excess vacancies is noted at high temperatures. These correlations made it feasible to obtain explicit dependencies of the strain-induced vacancy concentration on test variables such as the strain, strain rate, and temperature. These studies clearly reveal the power and utility of these NMR techniques in the determination of deformationinduced vacancies in situ in a noninvasive fashion.

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TDPAC studies on the recovery of Ag plastically deformed at room temperature

Cited by 6 publications

References 32 publications

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Perturbed angular correlation studies of uniaxial compressive stressed zinc, titanium, rutile, Ti₂AlN, and Nb₂AlC

In-situ nuclear magnetic resonance investigation of strain, temperature, and strain-rate variations of deformation-induced vacancy concentration in aluminum

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TDPAC studies on the recovery of Ag plastically deformed at room temperature

Cited by 6 publications

References 32 publications

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems

Perturbed angular correlation studies of uniaxial compressive stressed zinc, titanium, rutile, Ti2AlN, and Nb2AlC

In-situ nuclear magnetic resonance investigation of strain, temperature, and strain-rate variations of deformation-induced vacancy concentration in aluminum

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Perturbed angular correlation studies of uniaxial compressive stressed zinc, titanium, rutile, Ti₂AlN, and Nb₂AlC