Correct Answer - Option 1 : below the recrystallising temperature
Explanation:
Recrystallization Processes:
Recrystallization is a purification technique for solid compounds. Recrystallization is a process by which deformed grains are replaced by a new set of defect-free grains that nucleate and grow until the original grains have been entirely consumed and the crystal lattice structure of the metal becomes reoriented. Consequently, the metal becomes more workable and ductile.
Recrystallization temperature:
The recrystallization temperature is the temperature at which recrystallization can occur for a given material and processing conditions. This is not a set temperature and is dependent upon various factors like purity, grain size, cold worked and heating rate, etc. Some standard outcomes are given below.
- Increasing annealing time decreases recrystallization temperature
- Alloys have higher recrystallization temperatures than pure metals
- The increasing amount of cold work decreases recrystallization temperature
- Smaller cold-worked grain sizes decrease the recrystallization temperature
Note: The recrystallization temperature for steels is typically between 400°C and 700°C.
Cold Working:
If the metalworking process is carried out below its re-crystallization temperature, it is called cold working.
- In cold working, process metals are plastically deformed below their recrystallization temperature.
- In cold working hardness, yield strength increases but ductility decreases.
Examples: Bending, shearing, squeezing, etc.
Hot-working:
If the metalworking process is carried out above its re-crystallization temperature, it is called hot working.
- In hot working, process metals are plastically deformed above their recrystallization temperature.
- Hot-working improves the engineering properties of the workpiece because it replaces the microstructure with one that has fine spherical-shaped grains. These grains increase the strength, ductility, and toughness of the material.
Examples: Rolling, Extrusion, drawing, hot forging, etc.
