Dear Aman

In polycrystalline structures of metals /metallic alloys , point defects,i.e. substitution atoms, interstitial atoms,vacancies, or linear (lines)defects,i.e., screw and edge dislocations ,or planar defects,i.e., sracking fault are all crystallographic defects with different mobilities in the bulk of the polycrystalline structures.. For instance,point defects can move in the structure so readily without deformation,i.e., stresse or pressure, by diffusion from one location to another ,i.e.,dislocations,due to the concentration different between the two location,as a driving force for the diffusion mechanism. In contrast,dislocation lines can only move in the slip planes of the polycrastalline structures under deformation, even if the deformation is far less than the yield strength of the material of the structure. On the contrary, stacking faults ,i.e., partial dislocations ,require not only deformation but also specific stacking fault energy in order to move in the structure.

So,to answer your question,point defects attrack to dislocation lines due to naturally the space different which is available to the dislocation lines to accommodate point defects.

Hi,

Some experimental results on not so far mechanism in Ge dislocation here:

Article Study of Ge Threading Dislocations Post Growth Treatments

There's no physical attraction force extending over a distance of many lattice constants. However, when getting close to a dislocation, a point defect may get trapped by the dislocation's potential field. As point defects tend to move around a lot, many of them accidentally may get trapped by dislocations, which may appear like some sort of far field attraction.

Dislocations are strong perturbations of the crystal structure. They act as strong attractive potential (potential well) with respect to point defects.

Both dislocation and the point defect have stress fields, which are associated with strain energy. A point defect, in vicinity of a line defect may partially cancel out each other's stress field, thereby leading to reduction in elastic energy. Thus, the migration of a point defect towards a dislocation is energetically favorable.

@Amlan Dutta , the explanation sounds good. Is there any reference for the same?

Manoj Warrier , the following books incorporate the theory behind dislocation-point defect interaction:

(1) Theory of dislocations (Hirth and Lothe) - plz see chapter 14.

(2) Thermally activated mechanisms in crystal plasticity (Caillard and Martin) - Chap. 3, sec. 3.2 in particular.

(3) Dislocations and plastic deformation (Kovacs and Zsoldos) - Chap. 3, sec. 3.6.

You can also look for several studies performed through atomistic simulations, which have explored the interactions between dislocations and point defects. If we consider a point defect, say a vacancy - it can be shown to have a hydrostatic tensile stress. Therefore, it feels an effective attractive force towards an edge dislocation, where a region of compressive stress is present.