Question

A2. Precipitation hardening process is usually done with a 'solution-treatment; quenching; ageing' sequence. What is the reason for doing solution-treatment prior to ageing? How does the solution-treatment temperature affect the effectiveness of the precipitation hardening?

Answer 1

The solution-treatment prior to ageing is done because the heating an alloy at a suitable temperature long enough cause one or more constituents to enter into a solid solution which homogenously mixed with each other which is the major part of hardening a precipitate. This process is also known as homogenization.

If we are heating the alloy at lower than the suitable temperature it will reduce the chance of nucleation to occur. At a relatively high temperature (often just below the solubility limit) so that the kinetic barrier of surface energy can be more easily overcome and the maximum number of precipitate particles can form. Hence solution-treatment temperature affects the effectiveness of the precipitate hardening.