Mechanical Engineering - Engineering Materials - Discussion

Age hardening creates changes in physical and mechanical properties by producing fine particles of a precipitate phase, which impede the movement of dislocations, or defects in a crystal's lattice. Since dislocations are often the dominant carriers of plasticity, this serves to harden the material.

It is done for increasing yield point of malleable materials like Al-Cu alloys. After quenching from alpha phase to form a supersaturated solid solution, they are heated below solvus temperature to cause precipitation of fine particles of copper. This precipitates hinder the dislocation movement which increases hardness and strength. Thus they are also called precipitation hardening.

It is used to increase yield strength of malleable metals and their alloys.

What is age hardening?