Dislocation–solute cluster interaction in Al–Mg binary alloys

Abstract

The close-range interaction of dislocations and solute clusters in the Al-Mg binary system is studied by means of atomistic simulations. We evaluate the binding energy per unit length of dislocations to the thermodynamically stable solute atmospheres that form around their cores, at various temperatures and average solid solution concentrations. A measure of the cluster size that renders linear the relationship between the binding energy per unit length and the cluster size is identified. The variation of the interaction energy between a dislocation and a cluster residing at a finite distance from its core is evaluated and it is shown that the interaction is negligible once the separation is larger than approximately 15 Burgers vectors. The data are relevant for the dynamics of dislocation pinning during dynamic strain ageing in solid solution alloys and for static ageing.

Monte Carlo simulations of strain-driven elemental depletion or enrichment in Cu95Al5 and Cu90Al10 alloys

“…Similarly, the strain energy due to misfit is much relieved by small atoms (Cu) segregating to compressive sites. A similar segregation of large (small) atoms to the local tensile (compressive) strains field was also observed in alloy systems with negative heats of mixing [42][43][44][45][46]. Smaller Cu atoms in Al-Cu alloys were observed to segregate to the compressive regions of the extended dislocation dipole [42].…”

“…Smaller Cu atoms in Al-Cu alloys were observed to segregate to the compressive regions of the extended dislocation dipole [42]. In Al-Mg alloys, larger Mg atoms segregation to the tensile strain field of a split edge dislocation was observed, where the area below the stacking fault is under tension [43][44][45]. It also demonstrates that the precise composition and size control of nanostructures can be achieved by careful design of applied strain fields.…”

“…We propose that the SRO or clustering solute will provide significant solid-solution strengthening. Firstly, the solute clusters can contribute to significant strengthening, thereby providing effective resistance to slip dislocations, as well as to strain hardening and ductility, by increasing the dislocation storage capability [12,[42][43][44][45]49]. In fact, solute clustering has long been reported in conventional a Cu-Al alloys as well as nanostructured Al alloys engineered by severe plastic deformation and linked to strengthening [12,13,47].…”

A molecular dynamics study of self-diffusion in the cores of screw and edge dislocations in aluminum

“…The point-defect diffusion coefficient constitutes only one ingredient of the diffusion process, which must be combined with point-defect concentrations, jumpcorrelation factors and other ingredients to obtain D d [35]. For impurity diffusion, the equilibrium segregation and impurity-defect binding energies at different sites should also be known [10,34]. An alternative and more straightforward approach adopted in [4] is to extract D d from mean-squared atomic displacements computed by direct molecular dynamics (MD) simulations.…”

“…Deviations from the power law of creep can be attributed to dislocation diffusion [6,7]. Diffusion of solute atoms along arrested dislocations is one of the proposed mechanisms of dynamics strain aging in alloys exhibiting flow instabilities [8][9][10]. The kinetics of solute segregation to surfaces and grain boundaries can be enhanced by diffusion along dislocations terminating at the interfaces [11][12][13].…”