Understanding Age Hardening

Age hardening, also known as precipitation hardening, is a heat treatment technique used to increase the yield strength of malleable metal alloys.

It involves dissolving alloying elements in a matrix at a high temperature, followed by rapid cooling (quenching) and then heating to a lower temperature to allow fine precipitates to form, which impede dislocation movement.

Identifying Duralumin's Role

The question asks which material is related to age hardening.

• Age hardening is a process where metals become stronger over time (aging) after specific heat treatments.
• Duralumin is an alloy primarily of aluminum, copper, magnesium, and manganese. It is famously known for its ability to be strengthened significantly through age hardening.
• Cast iron is a high-carbon alloy of iron and silicon and does not typically undergo age hardening in the same way as aluminum alloys.
• Gun metal is a type of bronze (copper, tin, zinc) and while it can be heat treated, it's not the primary example associated with age hardening compared to Duralumin.
• German silver (nickel silver) is an alloy of copper, nickel, and zinc; it is typically strengthened by cold working, not age hardening.

Therefore, Duralumin is directly associated with age hardening.