Low-temperature anomalies in the plasticity of crystalline materials

Feltham, P.

doi:10.1002/pssa.2210750162

Cited by 21 publications

(4 citation statements)

References 12 publications

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“…However, at somewhat higher values of t, the σ /ln (t) curves flatten. These curves are basically logarithmic and in step with the relation proposed by Feltham [17] in his single barrier model of stress relaxation…”

Section: Resultssupporting

confidence: 77%

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Irradiation energy dependence of stress relaxation rate and activation volume in polycrystalline nickel

Ghauri¹,

Afzal²,

Raza³

2007

Phys. Scr.

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Stress relaxation in un-irradiated and electron beam irradiated polycrystalline nickel (99.99%) was studied at room temperature. The specimens were irradiated by high-energy electrons with energies in the range 8–18 MeV for 12 min at 300 K. The tensile tests of both un-irradiated and irradiated specimens were carried out at room temperature using a universal testing machine. During deformation, straining was frequently interrupted to observe stress relaxation at fixed loads. Measurements were made over the entire stress-strain curves up to fracture. The stress-relaxation was found to be logarithmic with time and its rate was found to decrease with an increase in the energy of incident electrons. The activation volume Vσ was observed to decrease with an increase in stress levels (σ0) both in un-irradiated and irradiated specimens, however Vσ values were higher in irradiated specimens than those of un-irradiated specimens. The intrinsic height of energy barrier (Uo) to the movement of dislocations increased with an increase in incident electron energy. The results are analysed in terms of a single barrier model of stress relaxation proposed by Feltham.

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Section: Resultssupporting

confidence: 77%

“…According to the single barrier model of stress relaxation [17], the activation energy U 0 for the movement of dislocations is correlated with the activation volume v σ associated with initial stress level σ 0 , and deformation temperature T as…”

Section: Resultsmentioning

confidence: 99%

Irradiation energy dependence of stress relaxation rate and activation volume in polycrystalline nickel

Ghauri¹,

Afzal²,

Raza³

2007

Phys. Scr.

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“…The empirical, exponential, form for the temperature dependence of f , previously used [19], represents the results rather well for all concentrations. The lower and…”

Section: Theory and Discussionmentioning

confidence: 91%

Solid-Solution Hardening

Feltham

Kauser

1990

phys. stat. sol. (a)

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The temperature and concentration dependences of the yield-stress are determined in the Cu/Zn system with polycrystalline brasses (0.03 to I .O at '10 Zn) and high-purity copper of the same grain size between 15 and 300 K. The data, as well as similar ones on other dilute copper alloys, given in the literature, are found to be well accounted for by the 'kink-pair-formation' model of solid-solution hardening, originally developed for concentrated solid solutions. At temperatures at which diffusional forms of recovery are absent, the model is shown to be applicable at all concentrations, with possiblc exceptions at levels below about 10-2%, and allows for the influence of work-hardening due to dislocations, present in the metal also in its solute-free 'ground state', on the process of solid-solution hardening. The kink-pair nucleation process is examined in dctail.Die Temperatur-und Konzentrationsabhangigkeiten der FlieMspannung wird im System Cu/Zn an Messing-Einkristallen 0,03 bis 1,0 At% Zn) und hochreinem Kupfer der gleichen KorngroDc im Bereich 15 bis 300 K bestimmt. Die Messungen, sowie gleichartige aus der Literatur entnommene Angaben iiber andere schwach legierte, auf Kupfer basierende feste Losungen, weisen auf die gute Anwcndbarkeit des Begriffes der Erzeugung von Kinkenpaaren, der friiher zur Erklarung der durch Legierung bedingten Verfestigung in konzentrierten festcn Losungen vorgeschlagen wurde, auch auf den Fall schwach legierter Metalle hin. Fur Temperaturen, bei denen keine diffusionsbedingte Erholung stattfindet zeigt sich das Modell bei allen Konzentrationen anwendbar; mogliche Ausnahmen diirftc man unter einem Niveau von ungefahr 10-20h erwarten. Die durch die Anwesenheit von Versetzungen bedingte mechanische Verfestigung, welche auch im legierungsfreien "Grundzustand" des Metalls vorhanden ist, wird im Modell beriicksichtigt. Einzelheiten des Kinkcnpaarbildungsprozesses werden erortert.

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“…The deviations from the monotonic τ -T behaviour are evident in the case of copper single crystals alloyed with 0.66, 0.95 and 2.95 at.%Ge below a certain temperature T specific to the alloy. As to the origin of this low-temperature anomaly, Feltham [20,21] considered it to be a consequence of the deformation-induced enhancement of local stresses, to levels above the applied stress, at barriers to the movement of dislocations at rather low temperatures (T < T ) where dynamic recovery processes will become increasingly inhibited. The applied stress appearing in the kinetic relations of deformation, e.g.…”

Section: Discussionmentioning

confidence: 99%

Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters

2008

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Abstract:The mode of planar distribution of solute atoms in Cu single crystals alloyed with 0.5 to 8.0 at.%Ge has been investigated via the temperature dependence of the critical resolved shear stress of these alloys. It is found that there exists a critical solute concentration ≈ 5 at.%Ge below which the distribution of solute atoms in the crystal is random, and above which some local ordering occurs. This together with such data available in the literature for Cu-Zn, Cu-Al and Cu-Mn alloys, i.e.≈ 27 at. %Zn, 7 at.%Al and 1 at.%Mn, when examined as a function of the size-misfit factor δ = (1/ )(d /d ) of a given binary alloy system, shows that the value of strongly depends on δ; the smaller the magnitude of δ, the greater the value of and vice versa. Also, the value of is found to correlate well with the electron-to-atom ratio ( / ) of the Cu-Zn, Cu-Al, Cu-Ge and Cu-Mn alloys with the solute concentration = . However, no systematic correlation exists between the critical solute concentration for the onset of local ordering and the modulus -mismatch parameter η = (1/G)(dG/d ).

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Low-temperature anomalies in the plasticity of crystalline materials

Cited by 21 publications

References 12 publications

Irradiation energy dependence of stress relaxation rate and activation volume in polycrystalline nickel

Irradiation energy dependence of stress relaxation rate and activation volume in polycrystalline nickel

Solid-Solution Hardening

Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters

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