The kinetics of a dislocation surmounting two different strength barriers

Arsenault, R.J.; Cadman, Theodore W.

doi:10.1002/pssa.2210240126

Cited by 22 publications

(6 citation statements)

References 7 publications

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“…that the effective average activation energy TGo of randomly distributed obstacles is larger than AGO of the single activation process. Computer simulation data of AG as a function of temperature, obtained by [6] show also this tendency. Though a quantitative result can be obtained by computer simulation with very arge arrays only the relation between the "measured" average activation energy and the activation energy of the single process mo x 1.2 AGO seems to be independent of the obstacle strength, which has been varied between Po = 0.05 and 0.6 [6, 12,131.…”

Section: Activation Energysupporting

confidence: 57%

“…To our knowledge only one curve of the stress dependence of the activation volume obtained by computer simulation has been published [6]. These data, drawn in Fig.…”

Section: Represent Values a T Relatively Low Temperaturesmentioning

confidence: 99%

“…The randomly distributed obstacles cause a higher activation energy. This means 2, Since the finite size of the arrays at computer simulations leads to an overestimation of t-values [6,7,9] especially at low temperatures [I31 the t-values at low temperature have been corrected by a simple estimation of the array size effect [19]. s, In real experiments the stress range in order to measure veup(t) at constant temperature is very limited due to the necessary changes of ic of many orders of magnitude.…”

Section: Activation Energymentioning

confidence: 99%

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Activation energy and activation volume of dislocation movement through randomly distributed point obstacles

Wielke

1981

Phys. Stat. Sol. (a)

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The macroscopic properties of the plastic deformation of a simple model crystal which obeys the Friedel relation are compared with computer simulation data and some in the literature unnoticed differences are discussed. It is pointed out that the random distribution of obstacles causes on average activation energy ΔG0, about 20% larger than ΔG0 of the single process of thermal activation. The activation volume and the average dislocation segment length l between obstacles is proportional to τ −1/3 only at low temperatures whereas at higher temperatures l calculated from computer simulation data increases more rapidly with decreasing stress than expected by the Friedel relation, l ∼τ1/3.

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Section: Activation Energysupporting

confidence: 57%

“…To our knowledge only one curve of the stress dependence of the activation volume obtained by computer simulation has been published [6]. These data, drawn in Fig.…”

Section: Represent Values a T Relatively Low Temperaturesmentioning

confidence: 99%

Section: Activation Energymentioning

confidence: 99%

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Activation energy and activation volume of dislocation movement through randomly distributed point obstacles

Wielke

1981

Phys. Stat. Sol. (a)

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“…In general, it turns out that the dislocation motion may indeed be characterized by an Arrhenius-type rate equation, but the activation enthalpy is a complicated function of stress, temperature and obstacle density and strength. The problem was approached analytically by Landau and Dotsenko [8] and Schlipf [9] for systems with random identical obstacles and by Arsenault and Cadman [10], Zaitsev and Nadgornyi [11] and Schoeck [12] for distributions of obstacles with two different strengths and activation enthalpies. These studies used various simplifying assumptions of which the most important is disregarding spatial correlations between obstacle failure events along given dislocation.…”

Section: Introductionmentioning

confidence: 99%

Thermally activated motion of dislocations in fields of obstacles: The effect of obstacle distribution

Picu

2007

Phys. Rev. B

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The thermally activated motion of dislocations across fields of obstacles distributed at random and in a correlated manner, in separate models, is studied by means of computer simulations. The strain rate sensitivity and strength are evaluated in terms of the obstacle strength, temperature and applied shear stress. Above a threshold stress, the dislocation motion undergoes a transition from smooth to jerky, i.e. obstacles are overcome in a correlated manner at high stresses, while at low stresses they are overcome individually. This leads to a significant reduction of the strain rate sensitivity. The threshold stress depends on the obstacle strength and temperature. A model is proposed to predict the strain rate sensitivity and the smooth-to-jerky transition stress. Obstacle clustering has little effect on strain rate sensitivity at low stress (creep conditions), but it becomes important at high stress.It is concluded that models for the strength and strain rate sensitivity should include higher moments of the obstacle density distribution in addition to the mean density.

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“…He concluded that the linear additivity at finite temperature did not follow from linear additivity at T = 0. Aresenault and Cadman [33] simulated the thermal motion of a dislocation across a random array of point obstacles having different strengths and zero-stress activation energies at finite temperature. Their simulations gave an overall flow stress σ (ε, T ) lying between σ 1 (ε, T ) + σ 2 (ε, T ) and (σ 2 1 (ε, T ) + σ 2 2 (ε, T )) 1/2 .…”

Section: Introductionmentioning

confidence: 99%

Thermally activated plastic flow in the presence of multiple obstacle types

Dong

2012

Modelling Simul. Mater. Sci. Eng.

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The rate- and temperature-dependent plastic flow in a material containing two types of thermally activatable obstacles to dislocation motion is studied both numerically and theoretically in a regime of relative obstacle densities for which the zero-temperature stress is additive. The numerical methods consider the low-density ‘forest’ obstacles first as point obstacles and then as extended obstacles having a finite interaction length with the dislocation, while the high-density ‘solute’ obstacles are treated as point obstacles. Results show that the finite-temperature flow stresses due to different obstacle strengthening mechanisms are additive, as proposed by Kocks et al, only when all strengthening obstacles can be approximated as point-like obstacles. When the activation distance of the low-density extended obstacles exceeds the spacing between the high-density obstacles, the finite-temperature flow stress is non-additive and the effective activation energy differs from that of the Kocks et al model. An analytical model for the activation energy versus flow stress is proposed, based on analysis of the simulation results, to account for the effect of the finite interaction length. In this model, for high forest activation energies, the point-pinning solute obstacles provide a temperature-dependent backstress σb on dislocation and the overall activation energy is otherwise controlled by the forest activation energy. The model predictions agree well with numerical results for a wide range of obstacle properties, clearly showing the effect due to the finite interaction between dislocation and the obstacles. The implications of our results on the activation volume are discussed with respect to experimental results on solute-strengthened fcc alloys.

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The kinetics of a dislocation surmounting two different strength barriers

Cited by 22 publications

References 7 publications

Activation energy and activation volume of dislocation movement through randomly distributed point obstacles

Activation energy and activation volume of dislocation movement through randomly distributed point obstacles

Thermally activated motion of dislocations in fields of obstacles: The effect of obstacle distribution

Thermally activated plastic flow in the presence of multiple obstacle types

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