Abstract
An approach to the study of the mechanisms of shear deformation in the bulk of face centered cubic (FCC) single crystals based on molecular dynamics simulation is proposed. Similar shear patterns obtained experimentally, and in simulations, allow consideration of the effect of crystallographic and geometric factors on deformation mechanisms. Deformation of <001> single-crystal samples in the form of tetragonal prisms with {110} and {100} lateral faces and different height-to-width ratios was studied. The simulation showed that the sample vertices are the preferential sites for shear initiation. It was found that the formation of deformation domains and interaction of shear planes are caused by the geometry of shear planes in the bulk of the single crystal, i.e., by their location in relation to basic stress concentrators and by their orientations relative to the lateral faces. The deformation patterns obtained in the simulations were in good agreement with those observed in the experiments. The fractions of sliding dislocations and dislocation barriers were determined for different materials, taking into account the crystallographic and geometric factors.
Highlights
When studying the mechanical behavior of materials subjected to plastic deformation, the main focus is on the determination of the yield strength and the analysis of strain hardening and plasticity.Dislocation glide within grains of polycrystals is usually distinguished from dislocation transmission through grain boundaries
The simulation results were obtained for a case very close to the equiprobable shear starting at all height-to-width ratios into domains depends largely on the geometry of positioning these basic eight concentrators
This ideal shear is difficult to realize in experiments because even small deviations in face parallelism or compression axis alignment. This is the main origin of the of failure to comply with the condition of the equiprobable shear along all four equiloaded planes, difference between the deformation patterns obtained in the experiments and molecular dynamics (MD) simulations
Summary
When studying the mechanical behavior of materials subjected to plastic deformation, the main focus is on the determination of the yield strength and the analysis of strain hardening and plasticity.Dislocation glide within grains of polycrystals is usually distinguished from dislocation transmission through grain boundaries. When studying the mechanical behavior of materials subjected to plastic deformation, the main focus is on the determination of the yield strength and the analysis of strain hardening and plasticity. It is reasonable to study the intragranular deformation mechanisms using single crystals that make it possible to calculate the shear stress given the direction of an applied load. In many cases a single crystal is considered to be homogeneous, with deformation propagating through the activation of heavily loaded sliding systems. It is supposed that the uniformly loaded systems can be activated throughout the entire bulk of the crystal. Deformation of a single crystal subjected to uniaxial compression (free settling) is noticeably inhomogeneous even for high symmetry orientations. The deformation non-uniformity is affected by the distribution irregularity of external stresses caused by the geometric shape of a sample and by the difference in shear conditions
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