3D Discrete Dislocation Dynamics Applied to a Motion of Low-Angle Tilt Boundaries

Abstract:

This paper presents a 3D discrete dislocation dynamics (DDD) model describing dislocation processes in crystals subjected to loadings at high temperatures. Smooth dislocations are approximated by short straight segments. Every segment is acted upon by a Peach-Koehler force obtained by summing up forces from all dislocation segments and a force due to the applied stress. The model addresses interactions between individual dislocations and rigid precipitates. The model is applied to a migration of low angle tilt boundaries (LATBs) characterized by different initial dislocation density and constrained by precipitates of different sizes. The calculations showed that, for applied shear stresses σ_xz lower than a certain threshold σ_crit.(h), the LATB is inhibited by the precipitate field. For σ_xz above σ_crit.(h), the LATB passes through the precipitate field. Some combinations of σxz and h lead to a decomposition of the LATB. The LATBs thus may evolve in three distinct modes depending on the initial microstructure. The threshold stress behaviour is known from creep tests of dispersion-strengthened NiCr alloys [1]. Furthermore, the critical stresses obtained from our calculations are below Orowan stresses for corresponding particle distribution. This behaviour has been also reported in creep experiments [1].

• Periodical: Key Engineering Materials (Volumes 592-593)
• Pages: 87-91
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.592-593.87
• Online since: November 2013
• Authors: Tomáš Záležák, Antonín Dlouhý
• Keywords: 3D Discrete Dislocation Dynamics, High Temperature Deformation, Low-Angle Dislocation Boundaries, Orowan Stress, Particle Strengthening

References

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