Mechanical Engineering - Engineering Materials - Discussion

Annealing consists of three stages mainly recovery, recrystallization and grain growth. In recovery, the stresses are reduced with the dislocations and further with recrystallisation the molecules recombine together or nucleate together and leads to grain growth.

When metal is heating to corresponding crystallization temperature of metal the internal stresses of metal are relieved then start re-crystallization that means forming of another crystal structure then metal will cooling during this process grain grow-thing is takes place.

After annealing the metal is heated above the crystallization temper and then stress relief.

The micro structure contains deformed grains from cold-work and there are a number of dislocations when we first heat the metal, for example, the additional thermal energy permits the dislocations to locomote.

This treatment removes residual stresses due to cold-working without changing the dislocation density of but causing a rearrangement in the dislocations therefore stress is relieved. Then new small grains begin to nucleate at the cell boundaries, eliminating most of the dislocations thereby creating the new grains we are recrystallizing the metal.

If the thermal energy is high enough the grains begin to grow, with favored grains consuming the smaller ones, therefore grain growth takes place.

After cold working of metals are subjected to annealing to relieve internal stresses are induced during cold working and that annealing carried out by subsequent re-crystallization and grain growth.

When heated steel 1st at of all relieves the internal stress caused by cold working and after it will be re crystallization of steel and than upper reaction. Temperature will be grain growth.

After annealing the metal is heated above the crystallization temper.

At the time of furnace cooling the metal relieves the stress and furnace cooling the grain size is increase.