Annealing process - remove internal stresses from a metal - Material Science

Q.  Which process is used to remove internal stresses from a metal?
- Published on 06 Aug 15

a. Annealing
b. Cold working
c. Both a. and b.
d. None of the above

ANSWER: Annealing
 

    Discussion

  • Sravanthi   -Posted on 06 Oct 15
    - Annealing is a process in which the metal is relieved from internal stresses. Metal is heated below melting point temperature and the metal losses its stored energy and comes back to strain-free condition. Recovery, recrystallization and grain growth are the methods by which metal losses its stored energy.

    - Annealing process alters physical and chemical properties of materials and increases ductility. It reduces hardness of the material. In this process, the material is heated above recrystallization temperature and cooled after maintaining it at suitable temperature.

    - In crystal lattice, atoms migrate and number of dislocations decrease which lead to changes in ductility and hardness.

    - In recovery stage, the material is softened and dislocations along with internal stresses are removed. This occurs at low temperatures before strain-free grains appear. Grains deformed by internal stresses are replaced by new strain-free which nucleate during recrystallization. Grain growth occurs if annealing process continues even after recrystallization.

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