Illustrate objectives of heat treatment processes

Heat treatment is normally adopted for the following:

(i) To refine grain structure

(ii) To improve machinability

(iii) To improve hardness and strength

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

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

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

(vii) To reduce corrosion rate.

(viii) To improve electrical and magnetic properties.

(ix) To soften metals for further (cold) working as in wire drawing or cold rolling.

(x) To homogenise structure; to remove coring or segregation.

(xi) To spheroidize tiny particles by diffusion.