What are the objectives of heat treatment processes?

The heat treatment is generally adopted for the following:

(i)  To refine grain structure

(ii) For better machinability

(iii)  For better hardness and strength

(iv)  For relieve internal stresses developed during cold working, welding, casting, forging etc.

(v)  To improve mechanical properties like tensile strength, ductibility and toughness etc.

(vi)  To enhance heat, wear and corrosion resistance of materials.

(vii)  To enhance corrosion rate.