Lösungshärten

Lösungshärten is a German term referring to a heat treatment process used to increase the hardness and strength of certain metal alloys, particularly those containing elements that can dissolve into a base metal at elevated temperatures and then precipitate out upon cooling. This process is also known in English as precipitation hardening or age hardening.

The fundamental principle involves two main stages. The first stage is solution treatment, where the alloy is heated to a temperature sufficient to dissolve the hardening elements into a solid solution within the base metal. This is typically followed by rapid cooling, often quenching in water or oil, to retain these dissolved elements in a supersaturated solid solution at room temperature.

The second stage is aging, where the quenched material is then heated to a lower temperature, below the solution treatment temperature, for a specific period. During aging, the dissolved elements begin to precipitate out of the supersaturated solid solution in the form of fine, dispersed particles. These precipitates impede the movement of dislocations within the metal's crystal structure, thereby increasing its hardness, yield strength, and tensile strength.

The effectiveness of lösungshärten depends on the alloy composition, the temperatures and times used for both solution treatment and aging, and the cooling rate. Different alloys require specific parameters to achieve optimal properties. Common applications include aluminum alloys, nickel alloys, and some steels.