What is another name for natural aging in metal treatment?

The term "natural aging" in metal treatment is commonly referred to as "precipitation hardening" or "age hardening," which is associated with the process wherein the strength and hardness of an alloy are increased through the formation of small particles within the metal matrix. Among the choices provided, precipitation heat treatment is the term most closely aligned with natural aging.

In precipitation heat treatment, alloying elements are dissolved and then precipitated out of the solid solution, typically during aging at certain temperatures. This process is crucial for achieving the desired mechanical properties in specific alloys, especially in aluminum and titanium-based materials. Natural aging occurs when the alloy is left at room temperature, allowing these precipitates to form gradually over time without the application of additional heat.

Solution heat treatment, quenching, and tempering refer to different processes that do not specifically denote natural aging. Solution heat treatment involves heating the alloy to dissolve soluble phases, quenching is a rapid cooling process to retain that solution state, and tempering is a heat treatment used to reduce brittleness and improve toughness after quenching. Thus, precipitation heat treatment is the most accurate term related to natural aging in this context.