Recovery, Recrystallisation and Grain Growth
Follow the sequence by which cold-worked metals reduce stored energy and rebuild their grain structure.
Stored energy after working
Plastic deformation raises dislocation density and stores energy. The deformed structure is strong but internally heterogeneous and often less ductile.
Recovery
Recovery rearranges and annihilates defects without replacing the grain structure. Electrical resistance and residual stress may fall before hardness changes substantially.
Recrystallisation
New strain-free grains nucleate and grow when temperature and time are sufficient. Prior strain, particle distribution and heating rate control the kinetics.
Grain growth
After recrystallisation, boundaries continue to move to reduce interfacial energy. Excessive growth reduces grain-boundary strengthening and may worsen toughness.
Engineering takeaway
Annealing is a competition among recovery, recrystallisation and growth; define the target grain size rather than only a furnace temperature.