Atomic-scale models for hardening in fcc solid solutions

Abstract

Atomic-scale simulations are associated with an elastic line model to analyze thoroughly the pinning strength experienced by an edge dislocation in some face centered cubic (fcc) solid solutions, Al(Mg) and Ni(Al) with solute concentration comprise between 1 and 10 at. %. The one-dimensional elastic line model is developed to sketch out the details of the atomic-scale. The account of such details is shown to yield a proper description of the dislocation statistics for the different systems. The quantitative departure between hardening in Al(Mg) and Ni(Al) is then demonstrated to hinge on the difference in the short range interaction between the partial dislocations and the isolated impurities. It is also shown that an accurate description of the solid solution hardening requires the account for the dislocation geometry and the dislocation interaction with clusters of solute atoms. The elastic line model allows us to perform some computations at the microscopic scales meanwhile accounting for the most important atomic details. A comparison with experimental data is attempted.

Solute strengthening in random alloys

“…This accounts for the interaction energy U n γ1 of the solute with the stacking fault over the two planes adjacent to the glide plane that define the stacking fault plane. Note that interactions of substitutional solutes in planes farther away from the stacking fault can exists [37] and can be included in Eq. (29) by considering j = ±2, 3, .... Interstitial solutes and/or multiple solute sites not related by symmetry [76,77] are also straightforward to consider.…”

“…Numerical simulations of solute strengthening has lead to the identification of important trends and understandings: contribution to the strength of solutes in planes away from the glide plane, role of the screw vs. edge dislocations, role of solute pairs when the solute concentration increases and the reference is taken from a pure elemental matrix, etc. [37,38,81,109,110]. However, MD simulations, even using empirical potentials, suffer from important limitations, which make difficult to compare simulation results to (i) analytical models and (ii) real material strength.…”

“…The Friedel-type models entirely neglect the longrange interactions, so that even solutes just two atomic planes above or below the glide plane are not considered to exert forces on the dislocation even though their maximum pinning force can be appreciable [37]. If such solutes were included, the Friedel theory would need to include different values for F max for each atomic plane and, moreover, the "spacing" between solutes would become very small so that the dislocation bow out would be occurring over atomic distances where the line tension model surely fails.…”

Displacement field of a screw dislocation in a〈011〉Cu nanowire: An atomistic study

“…4,16 It contributes to maintain the two partials separated at a nanometer distance in copper. The modification made on r c (i.e., r c = √ 3r 0 ) in the present SMA potential leads to γ SF ≈ 55 mJ m −2 (while 45 mJ m −2 is found experimentally 4 and the value of 44.4 mJ m −2 is obtained by Mishin et al 17 ).…”

Robust atomistic calculation of dislocation line tension

“…The Peierls stress, usually measured on a straight dislocation, is either treated as a uniform applied internal back stress so that the effective applied stress is τ app − τ P or is neglected. After such adjustments/corrections, however, the literature values for the line tension of an edge dislocation in Al using the Ercolessi-Adams (EA) EAM potential range from 0.06 ≤ Γ ≤ 1 eV/Å [2,20,42,44]. Since the CRSS τ c is directly proportional to Γ, per eq.…”