The movement of dislocations under applied stress leads to what kind of deformation?

• A. Plastic deformation
• B. Elastic deformation
• C. Brittle fracture
• D. Phase transformation

Answer: (A)

Dislocations moving under applied stress produce plastic deformation, a permanent change in shape that remains after the load is removed. When a dislocation glides along a slip plane, atoms shift incrementally and the material undergoes irreversible shear. This is the defining feature of plasticity: the deformation persists because the lattice has been permanently rearranged.

Elastic deformation, by contrast, is reversible—atoms are displaced only temporarily, and the material returns to its original shape when the stress is released, with no lasting slip. Brittle fracture is a failure process involving crack initiation and rapid propagation, not a smooth, permanent shape change from dislocation glide. Phase transformation involves a change in crystal structure, which is a different kind of structural change than the slip-driven permanent deformation described here.