What are the typical steps in precipitation hardening (age hardening)?

• A. Solution treatment, quenching, aging
• B. Annealing, cold working, aging
• C. Solution treatment, aging, quenching
• D. Quenching, aging, solution treatment

Answer: (A)

In precipitation hardening, you first dissolve the alloying elements to form a uniform solid solution, then trap that state by rapid cooling, and finally allow fine precipitates to form during aging. This sequence—solu­tion treatment, quenching, then aging—creates a supersaturated solid solution that, when aged, precipitates as tiny particles that block dislocations and increase strength.

If aging were done before dissolving and trapping the solute, or if you tried to age without first forming a supersaturated solid solution, the precipitates would be uncontrolled or absent, and the strengthening would be much weaker. Similarly, skipping the solution treatment or choosing a different order would not produce the fine, well-dispersed precipitates that give the characteristic hardness gain of age hardening.