Explanation: In the process of annealing, the crystal goes through three stages which are called recovery, recrystallization and grain growth in order.

Explanation: When a body is plastically deformed at low temperatures compared to its melting point, we observe micro structural changes like change in grain growth, strain hardening and increase in dislocation density.

Explanation: Recovery occurs at a lower temperature than recrystallization or grain growth. Recovery takes place at the temperature below 0.3Tm.

Explanation: Recovery is subdivided into two parts, strain-relief crystallization and polygonization. Strain-relief crystallization occurs when deformed metals are heated and the latter takes place under certain conditions.

Explanation: After strain-relief crystallization, the hardness and the strength of the material decrease by 10-15% from their original value. On the other hand, ductility increases by that percentage.

Explanation: Polygonization is the process in which new grain boundaries are formed and isn’t common for all metals and observed after slight deformation. In copper and its alloy, this process rarely develops.

Explanation: In recrystallization new grains are formed with small nuclei and they grow until they cover the whole parent material. Therefore, the new grain structure is fine and hence the grain structure is refined.

Explanation: For commercially pure iron, the lowest temperature at which recrystallization can occur is equal to 450°C. For aluminium and copper, it is equal to 100°C and 270°C respectively.

Explanation: The surface energy decreases during grain growth because of which free energy decreases. The grain starts growing and grain growth accelerates with increase in temperature.