Recrystallization temperature is one at which

Question

Question

This question was previously asked in

ESE Mechanical 2018 Official Paper

crystals first start forming from molten metal when cooled
new spherical crystal first begins to form from the old deformed ones when that strained metal is heated
the allotropic form changes
crystals grow bigger in size

Answer 1

Explanation:

When a material is cold worked its microstructural properties get changed. The property may revert back to the precold-worked states when they are given heat treatment or annealing treatment precisely. The restoration of the properties results through the following process

Recovery:

During recovery, the internal energy which was stored is relieved by virtue of dislocation motion due to atomic diffusion at the elevated temperature.

Recrystallization

It is a process accomplished by heating whereby deformed grains are replaced by a new set of grains that nucleate and grow until the original grains have been entirely consumed. During recrystallization, the mechanical properties that were changed as a result of cold working are restored to the precold-worked values.

Recrystallization temperature:

Grain growth:

Once the recrystallization is done the strain-free grains continue to grow if the metal is still at elevated temperature.