What does high stacking fault energy mean?
The equilibrium width is thus partially determined by the stacking-fault energy. When the SFE is high the dissociation of a full dislocation into two partials is energetically unfavorable, and the material can deform either by dislocation glide or cross-slip.
What is meant by stacking fault?
In crystallography, a stacking fault is a planar defect that can occur in crystalline materials. Crystalline materials form repeating patterns of layers of atoms. Errors can occur in the sequence of these layers and are known as stacking faults.
What are the implications of a higher or lower SFE?
High SFE would result in smaller dislocation core size (consider a dislocation as a pipe, and its diameter is the core size). Lower SFE means otherwise of course. In each case a metal behaviour changes dramatically. Higher SFE means generation of dislocations is more difficult, but dislocation mobility becomes easier.
What are stacking faults in silicon?
Stacking faults are crystallographic defects in which the proper order of stacking planes is interrupted. For example, consider the first three atomic planes or layers of a (111) silicon film. Each of these planes may be imagined to be a close-packed array of atomic spheres (Fig.
What is stacking sequence in FCC?
The FCC structure is made up of layers of octahedral,-type planes. These stack in a sequence ABC ABC as shown in fig. 3a. A, B and C are atom center sites relative to a close packed layer.
How are twins related to planar stacking faults?
Twins are also planar defects but are comprised of at least two adjacent stacking faults . They reorient the lattice and introduce a twin boundary , . Consequently, for the same strain, these three defects do not lead to the same texture, slip activity and deformation response.
When is a monolayer stacking fault is formed?
When a single leading partial is emitted and propagates across the grain to the opposing grain boundaries without subsequent nucleation of the trailing partial, then a monolayer stacking fault has formed. On the other hand, when the trailing partial nucleates from the same source, it corrects the stacking fault and recovers the original stacking.
How are perfect dislocations related to stacking faults?
Perfect dislocations are linear defects that do not change the lattice orientation as they glide. Shockley partial dislocations create stacking faults as they glide, and these stacking faults are planar defects in which the fcc stacking sequence has been altered.