Temperature and Stress Dependence of Mobility of Screw Dislocation in BCC Iron

2016 ◽  
Vol 258 ◽  
pp. 17-20
Author(s):  
Hideki Mori
Keyword(s):  
Screw Dislocation ◽  
Unit Length ◽  
Peierls Stress ◽  
Body Centered Cubic ◽  
Entropy Term ◽  
Energy Gradient ◽  
Bcc Iron ◽  
Peierls Barrier ◽  
Entropic Effect ◽  
Increasing Temperature

The Peierls stress and barrier of a screw dislocation in body-centered cubic iron at finite temperature is investigated by using the free energy gradient method. The Peierls barrier is shown to decrease from 12 to 5 meV per unit length of the Burgers vector with increasing temperature from 0 to 400 K. The entropy term of the Peierls barrier is estimated to be 0.2kB. The Peierls stress also decreases from 900 to 400 MPa with increasing temperature from 0 to 300 K. The change in the Peierls stress due to the entropic effect is larger than that of the Peierls barrier because of thermal softening.

scholarly journals The Properties of Shuffle Screw Dislocations in Semiconductors Silicon and Germanium

2015 ◽  
Vol 9 (1) ◽  
pp. 10-13 ◽  
Author(s):  
Huili Zhang ◽  
Chun Zhang ◽  
Chunhua Zeng ◽  
Lumei Tong
Keyword(s):  
Screw Dislocation ◽  
Peierls Stress ◽  
Diamond Structure ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Peierls Barrier ◽  
Silicon And Germanium

The dislocation widths, Peierls barriers and Peierls stresses for shuffle screw dislocations in diamond structure crystals, Si and Ge, have been calculated by the improved P-N theory. The widths are about 0.6b, where b is the Burgers vector. The Peierls barrier for shuffle screw dislocation in Si and Ge, is about 3.61~4.61meV/Å and 5.31~13.32meV/Å, respectively. The Peierls stress is about 0.28~0.33GPa and 0.31~0.53GPa, respectively. The calculated Peierls barriers and stresses are likely the results of shuffle screw dislocation with metastable core which is centered on the bond between two atoms.

Core energy and Peierls stress of a screw dislocation in bcc molybdenum: A periodic-cell tight-binding study

2004 ◽  
Vol 70 (10) ◽  
Author(s):  
Ju Li ◽  
Cai-Zhuang Wang ◽  
Jin-Peng Chang ◽  
Wei Cai ◽  
Vasily V. Bulatov ◽  
...  
Keyword(s):  
Screw Dislocation ◽  
Tight Binding ◽  
Binding Study ◽  
Peierls Stress ◽  
Periodic Cell ◽  
Core Energy

scholarly journals Screw dislocation structure and mobility in body centered cubic Fe predicted by a Gaussian Approximation Potential

2018 ◽  
Vol 4 (1) ◽  
Author(s):  
Francesco Maresca ◽  
Daniele Dragoni ◽  
Gábor Csányi ◽  
Nicola Marzari ◽  
William A. Curtin
Keyword(s):  
Screw Dislocation ◽  
Dislocation Structure ◽  
Gaussian Approximation ◽  
Body Centered Cubic

On non-glide stresses and their influence on the screw dislocation core in body-centred cubic metals I. The Peierls stress

1984 ◽  
Vol 392 (1802) ◽  
pp. 145-173 ◽  
Keyword(s):  
Screw Dislocation ◽  
Applied Stress ◽  
Strong Dependence ◽  
Dislocation Core ◽  
Peierls Stress ◽  
Exact Nature ◽  
Theoretical Shear Strength ◽  
Stress Variation ◽  
Cubic Model ◽  
Model Lattice

The response of the screw dislocation core in a body-centred cubic model lattice to a general applied stress tensor is examined by means of computer simulation. The Peierls stress is found to have the symmetry required by Neumann’s principle but is found also to have a very strong dependence on shear components of the applied stress which should not interact with the screw dislocation. Rather than having the constant value suggested by the Schmid law of critical resolved shear stress, the Peierls stress can vary from zero to the theoretical shear strength of the lattice, depending upon the exact nature of the critical applied stress components. Calculations with different interatomic binding potentials show that the Peierls stress variation, while different in detail, remains broadly the same, suggesting an origin in the dislocation core geometry rather than the specific charac­teristics of the force laws. Specialization to the case of uniaxial applied stress shows that the similar Peierls stress variation can nevertheless lead to quite different orientation dependences of the flow stress in different materials. Applications to the problem of brittle fracture and possible sources of the Peierls stress variation are discussed briefly.

Atomistic simulation for configuration evolution and energetic calculation of crack in body-centered-cubic iron

2006 ◽  
Vol 21 (10) ◽  
pp. 2542-2549 ◽  
Author(s):  
Li-Xia Cao ◽  
Chong-Yu Wang
Keyword(s):  
Low Temperatures ◽  
Crack Tip ◽  
Dislocation Nucleation ◽  
Effect Of Temperature ◽  
Body Centered Cubic ◽  
Partial Dislocations ◽  
Higher Temperature ◽  
Crack Blunting ◽  
Increasing Temperature ◽  
Extended Dislocation

The molecular dynamics method has been used to simulate mode I cracking in body-centered-cubic iron. Close attention has been paid to the process of the atomic configuration evolution of the cracks. The simulation shows that at low temperatures, partial dislocations are emitted before the initiation of crack propagation, subsequently forming the stacking faults or multilayer twins on {112} planes, and then brittle cleavage and extended dislocation nucleation are observed at the crack tip accompanied by twin extension. These results are in agreement with the experimental observation that twinning and fracture processes cooperate at low temperatures. Furthermore, an energetics analysis has been made on the deformation behavior observed at the crack tip. The effect of temperature on the fracture process is discussed. At the higher temperature, plastic deformation becomes easier, and crack blunting occurs. With increasing temperature, the fracture resistance increases, and the effect of the lattice trapping can be weakened by thermal activation.

scholarly journals Molecular Dynamics Simulation Study of the Mechanical Properties of Nanocrystalline Body-Centered Cubic Iron

Surfaces ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 381-391
Author(s):  
Jan Herman ◽  
Marko Govednik ◽  
Sandeep P. Patil ◽  
Bernd Markert
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Strain Rate ◽  
Tensile Tests ◽  
Dynamics Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
Bcc Iron ◽  
Average Grain Size ◽  
Study Results

In the present work, the mechanical properties of nanocrystalline body-centered cubic (BCC) iron with an average grain size of 10 Å were investigated using molecular dynamics (MD) simulations. The structure has one layer of crystal grains, which means such a model could represent a structure with directional crystallization. A series of uniaxial tensile tests with different strain rates and temperatures was performed until the full rupture of the model. Moreover, tensile tests of the models with a void at the center and shear tests were carried out. In the tensile test simulations, peak stress and average values of flow stress increase with strain rate. However, the strain rate does not affect the elasticity modulus. Due to the presence of void, stress concentrations in structure have been observed, which leads to dislocation pile-up and grain boundary slips at lower strains. Furthermore, the model with the void reaches lower values of peak stresses as well as stress overshoot compared to the no void model. The study results provide a better understanding of the mechanical response of nanocrystalline BCC iron under various loadings.

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