Dislocations and deformation
Strengthening of metallic alloys Microstructure influence on plastic deformation

When a metal is subjected to external stress, deformation occurs. At low stresses, deformation is reversible. This is called elastic deformation, and is the direct result of atomic interactions. The sample returns to its initial shape and dimensions when the stress is released.

Beyond a critical value of the applied stress, permanent deformation - plastic deformation - occurs. The yield strength corresponds to this critical stress. The value of yield strength depends on the alloy's composition and microstructure. The latter, in turn, is governed by the chemical composition and by the thermal or thermomechanical treatments imposed throughout the metal manufacturing process and during shaping of the ready-to-use part.