Solution treatment refers to a heat treatment process in which an alloy is heated to the high-temperature single-phase region and held at constant temperature, so that the excess phases are fully dissolved into the solid solution, followed by rapid cooling to obtain a supersaturated solid solution.

It is also known as solution quenching because its operation is similar to quenching. It applies to alloys with a solid solution matrix whose solubility changes significantly with temperature. The alloy is first heated to a suitable temperature above the solubility curve and below the solidus line and held for a certain period, allowing the second phases to dissolve into the solid solution. It is then rapidly cooled in water or other media to suppress re-precipitation of the second phases. As a result, a supersaturated solid solution at room temperature, or a solid-solution phase that normally exists only at high temperatures, can be obtained. Thermodynamically, this structure is metastable. It will undergo precipitation or other transformations under appropriate temperature or stress conditions. Generally, it serves as a preparatory heat treatment to create optimal conditions for subsequent heat treatment.