Question

what is difference between aging and tempering?

Answer 1

They differ mainly in objective. The science behind each is also quite different.

Aging is the process of heating a metal and allowing the natural kinetics of the metal to allow second phase allow particles to distribute themselves along slip planes, thereby increasing the tensile strength of the allow.

Tempering is the process of heating a metal to allow an increase in grain size. This increase increases the toughness, reduces the hardness, and reduces the tensile strength. It is commonly used in conjunction with hardening. The hardening creates very small grains and random dislocations, but yields very brittle material. Tempering allows us to relieve the brittleness without sacrificing too much of the tesile strength gained during hardness.

Answer 2

@eashmore
dear fellow, In tempering of martensite, when you will increase temperature then carbon will precipitate out from martensite structure and due to precipitation hardening will increase hardenss....
in aging and tempering, both we have super saturated solid solution, we heat them, second phase precipitate out causing increase in hardness, then more temperature and time will increase grain size, which will lead to decrease in hardness.......