What is age hardening? explain process for age hardening a material. what happens if we age the material for a very long time?

Age hardening is a process for strengthening of Non ferrous material. It is heat treatment technique follows 3 step.
In 1st step solutionizing is being that means heated the alloy in single phase region.
In 2nd step quenching should be done that is very fast colling from single phase region.
In 3rd step ageing that means we have to put the system for a certain period of time. That leads to formation of fine particles known as gp zone.

If we age more time in that situation size of particle increses which leads to decrease the strength.