Materials Science and Engineering Practice Exam

Relieving internal stresses is the main outcome of annealing. When a metal has been worked or deformed, it stores dislocations and residual stresses. Heating to an elevated temperature lets atoms move enough for dislocations to rearrange and annihilate, and for new, strain-free grains to form (recrystallization). This reduces the internal stress state, softens the material, and increases ductility, which is why annealing is used to restore formability after prior work.

The other effects don’t fit as the primary outcome: annealing generally softens rather than hardens the metal, increases or at least restores ductility rather than decreases it, and grain size behavior can vary but is not the defining result of annealing.