There are metals that fall under the classification of precipitation hardening. When quenching is performed upon some precipitation hardening-alloy, alloying elements of this alloy are trapped within solution, which results in soft metal. Performing aging for a solutionized-metal allow alloying elements for diffusing via microstructure & forming inter-metallic particles. Such particles nucleate & fall-out of the solution, act as reinforcing phase and increase alloy`s strength. There are two ways for aging of alloys. One is naturally aging in which precipitates are formed at the room temperature. Other is artificial aging in which elevated temperatures are used for making of precipitates. Both these aging ways have their own realities. Sometimes, alloys with natural aging ate stored within a freer for preventing them from becoming hard until after some further operations, for example rivets` assembly may become easy with soft alloy. Examples of the precipitation hardening-alloys include 7000 series, 6000 and 2000 series aluminum-alloy plus some super alloys and some alloys in the form of stainless steels. Hardened steels followed by aging are commonly known as the maraging steels which have resulted from martensite-aging term.