I'm not sure if you can read this Jake, but the reason it is called "precipitation hardening" and not plain "heat treatments hardening" is because there two ways to harden metals which both use heat treatments to regulate the amound of hardening.

Precipitation hardening uses the effects of enclosed dissimilar metal inside a base metal. Here the heat treatment affects the size, shape and distribution of the enclosures.

Plain heat treatment hardening (English name ?) use the ability of a certain metals to change their own metal structure to different forms. These changes are nearly always the results of temperature. As such there is no need for any alloy elements and as such it is a different hardening method to precipitation hardening. A good example of this plain hear hardening is normal iron/steel. Heat it and then cool it very rapidly and it will became very hard (and brittle). This can then be soften again by mildly heating it for a given period of time at a lower temperature. Allowing portions of the dissimilarity to morph back to less hard grid structures.

Wouter