Cross-slip in face-centered cubic metals: a general Escaig stress-dependent activation energy line tension model

Malka-Markovitz, Alon; Mordehai, Dan

doi:10.1080/14786435.2017.1406194

Cited by 24 publications

(17 citation statements)

References 32 publications

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“…Based on this work, Liu et al [19] developed a variational line tension model for cross slip, which was in better quantitative agreement with respect to the results based on nudged elastic band model. Recently, Malka-Markovitz and Morderhai [12,13] proposed a line tension model to describe the cross-slip energy barrier as a function of the stress state, which was also in in agreement with previous atomistic results [20].…”

Section: Introductionsupporting

confidence: 84%

“…Furthermore, it should be noticed that the estimation of the entropic barrier combining eqs. (12) and (16), with T m = 933 K, follows the trend of the MD simulation results, indicating that the MN compensation rule also holds for the biaxial case.…”

Section: Coupled Stressessupporting

confidence: 65%

“…This process is thermally-activated [5] and, hence, it depends on the magnitude of the energy barrier associated with the event. This energy barrier in FCC crystals varies with the Escaig and Schmid stresses [10,11,9,12,13]. The Escaig stress acts on the edge component of the Shockley partial dislocations, and controls the distance between them.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the stress state on the cross-slip free energy barrier in Al: An atomistic investigation

et al. 2020

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The influence of the stress state on the cross-slip rate in Al was analyzed by means of molecular dynamics simulations and transition state theory. The activation energy barrier in the absence of thermal energy was determined through the nudged elastic band method while the cross-slip rates were determined using molecular dynamics simulations for different magnitudes of the Schmid stress on the cross-slip plane, and of the Escaig stresses on the cross-slip and glide planes. The enthalpy barrier and the effective attempt frequency were determined from the average rates of cross-slip obtained from the molecular dynamics simulations. It was found that the different stress states influence the cross-slip rate assuming harmonic transition state theory. Moreover, the theoretical contributions to the enthalpy barrier (configurational and due to the interaction of the applied stress with the local stress field created by the defect) were identified from the atomistic simulations while the entropic contribution to the activation energy could be estimated by the Meyer-Neldel rule. Based on these results, an analytical expression of the activation enthalpy for cross-slip in Al as a function of the different combinations of Schmid and Escaig stress states was developed and validated. This expression can be easily used in dislocation dynamics simulations to evaluate the probability of cross-slip of screw dislocation segments.

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Section: Introductionsupporting

confidence: 84%

Section: Coupled Stressessupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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Influence of the stress state on the cross-slip free energy barrier in Al: An atomistic investigation

et al. 2020

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“…A similar argument as that used by Essmann and Mughrabi [35] suggests that below a critical separation in the direction normal to the slip plane, the screw segments will tend to cross slip and annihilate, further hindering plastic deformation. The orientation dependence of cross slip [36][37][38] may then be responsible in part for the scatter in the mean slip line spacings. Furthermore, for any single band there is also a variation in the spacings that arises from spatial variations in the precipitate distribution and the random nature of the double cross slip events during the formation process.…”

Section: Deformation Behaviourmentioning

confidence: 99%

A multiscale study on the morphology and evolution of slip bands in a nickel-based superalloy during low cycle fatigue

et al. 2020

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Plastic deformation during low cycle fatigue in fcc materials with low stacking fault energy is accumulated in slip bands, which become preferential sites for crack initiation. Whilst these dislocation structures have been studied before, little has been done to assess the effect and evolution of the individual slip lines within them. In this study, samples of a γ precipitate strengthened nickel-based superalloy are fatigued at room temperature and 700 • C for 1, 40 and 500 cycles. The resulting dislocation structures are characterised via Electron Channeling Contrast Imaging and Transmission Electron Microscopy. We introduce a new methodology to measure slip band parameters such as the slip line spacing and shear step length by analysing the holes left by sheared precipitates in γ -etched secondary electron micrographs. Statistics of these parameters are obtained and compared for different conditions. Advantages of this technique include resolution at the scale of individual planes, acquisition of true three-dimensional data and applicability in the bulk of the material. The combination of these techniques provides a unique mechanistic and quantitative insight into the slip band and precipitate morphology evolution.

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“…Different DDD codes consider different forms for the free-energy barrier ( ). Most codes consider only the Schmid stresses (glide stresses) on the slip plane ℎ. for an immobile dislocation, assuming that the activation energy is obtained from mainly from constricting the partial dislocations and it decreases linearly with this stress component: Recently, we proposed an expression for the stress dependent activation free energy barrier [19,20]. In this model, which is a line-tension model, we employed a harmonic approximation (HA) for the interaction energy between the partial dislocations and The free-energy barrier implemented in the DDD simulation relies on the line tension model [20].…”

mentioning

confidence: 99%

A molecular dynamics-informed probabilistic cross-slip model in discrete dislocation dynamics

2021

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We present here a quantitative study of dislocation cross-slip, an essential thermally activated process in deformation of metals, in discrete dislocation dynamics (DDD) simulations. We implemented a stressdependent line-tension model in DDD simulations, with minimal information from molecular dynamics (MD) simulations. This model allows reproducing in DDD simulations the probabilistic cross-slip rate calculated in MD simulations for Cu in a large range of stresses and temperatures. This model opens new horizons in modelling cross-slip related mechanisms such as deformation softening, dislocation-precipitate interaction and dislocation patterning in realistic strain rates.

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Cross-slip in face-centered cubic metals: a general Escaig stress-dependent activation energy line tension model

Cited by 24 publications

References 32 publications

Influence of the stress state on the cross-slip free energy barrier in Al: An atomistic investigation

Influence of the stress state on the cross-slip free energy barrier in Al: An atomistic investigation

A multiscale study on the morphology and evolution of slip bands in a nickel-based superalloy during low cycle fatigue

A molecular dynamics-informed probabilistic cross-slip model in discrete dislocation dynamics

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