Mumbai University > Mechanical Engineering > Sem 4 > Material Technology

Marks: 5M

Year: May 2015

• Recrystallization is a process by which deformed grains are replaced by a new set of undeformed grains that nucleate and grow until the original grains have been entirely consumed.
• Recyrstallisation annealing is an annealing process applied to cold-worked metal to obtain nucleation and growth of new grains without phase change. This heat treatment removes the results of the heavy plastic deformation of highly shaped cold formed parts. The annealing is effective when applied to hardened or cold-worked steels, which recrystallise the structure to form new ferrite grains.
• Recrystallization is usually accompanied by a reduction in the strength and hardness of a material and a simultaneous increase in the ductility.
• Thus, the process may be introduced as a deliberate step in metals processing or may be an undesirable byproduct of another processing step.
• The most important industrial uses are the softening of metals previously hardened by cold work, which have lost their ductility, and the control of the grain structure in the final product.
• Recrystallization is defined as the process in which grains of a crystal structure come in new structure or new crystal shape.
• A precise definition of recrystallization is difficult to state as the process is strongly related to several other processes, most notably recovery and grain growth.
• In somecases it is difficult to precisely define the point at which one process begins and another ends.

• "The formation of a new grain structure in a deformed material by the formation and migration of high angle grain boundaries driven by the stored energy of deformation".
• The rate of the microscopic mechanisms controlling the nucleation and growth of recrystallized grains depend on the annealing temperature