Question

How and why do heat treatments change the microstructure? (diffusion-austentizing “solid solution”)

Answer 1

Heat-treating is a term used to describe all of the controlled heating and cooling operations performed on a material in the solid state for the purpose of altering its microstructure and/or properties.

Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, normalizing and quenching

The major objectives of the different kinds of thermal treatments are:

1. Soften the material for improved workability.
2. Increase the strength or hardness of the material.
3. Increase the toughness or resistance to fracture of the material.
4. Stabilize mechanical or physical properties against changes that might occur during exposure to service environments.
5. Insure part dimensional stability.
6. Relieve undesirable residual stresses induced during part fabrication.

Source : NDT