What does the term 'recrystallization temperature' refer to?

The term 'recrystallization temperature' refers specifically to the temperature at which new grains form in a deformed metal. During the process of recrystallization, the internal structure of the metal is changed, allowing for the formation of new grains that are free of the dislocations and defects introduced during previous deformation processes. This occurs after the metal has been work-hardened, and the recrystallization allows the metal to regain ductility and reduce hardness.

Achieving this temperature is crucial for processing metals, as it enables materials to undergo further shaping and working without the brittleness associated with higher strength and lower ductility. Following recrystallization, the improved grain structure leads to enhanced mechanical properties and overall performance in applications where the metal will be subjected to stress or bending.

In contrast, the other options pertain to different temperature-related phenomena that do not specifically define recrystallization. For example, melting temperature indicates phase transitions from solid to liquid, while plastic deformation temperature relates to the limits of ductility before permanent changes occur in shape and structure. Meanwhile, the temperature for thermal expansion deals with the general response of materials to temperature increases, which does not involve recrystallization processes.