During recrystallization (hot working), what is the typical effect on defect density, strength, and ductility?

• A. Defect density increases; strength increases
• B. Defect density decreases; strength decreases; ductility increases
• C. Defect density decreases; strength increases
• D. Defect density increases; ductility decreases

Answer: (B)

Recrystallization during hot forming relieves the stored deformation energy by forming new, strain-free grains. The high dislocation density created by prior deformation is largely removed as these new grains nucleate and grow, so defect density decreases. With fewer dislocations to impede motion and no work-hardening obstacles, the material softens, so strength decreases, while the ease of plastic deformation increases, giving higher ductility. Temperature can also promote some grain growth, which can influence strength, but the overall trend after recrystallization is softening and increased ductility.