Temperature and Soaking Time
Heating Phase: The alloy is heated to a temperature within a specific range, typically above the solvus temperature— the temperature at which the alloying elements go into solution— but always below the eutectic melting temperature (fusion start temperature) typically by 5° to 8°C (10° to 15°F). Heating rate is sometimes critical to specific processes or alloys.
Temperature Ranges: The temperature varies based on the alloy composition, the type of product or the fabrication process of the material. However, the common temperature range is typically between 455°C to 565°C (850°F to 1050°F).
Soaking Time: The alloy is held at this elevated temperature for a specific duration to allow for the dissolution of alloying elements into the aluminum matrix. The soaking time varies based on the alloy composition, the type of product or the fabrication process and the section thickness of the material.
Quenching Phase
Rapid Cooling: After the soaking period, the alloy is rapidly cooled or quenched.
Quenching involves using a suitable medium, such as water, polymer quenchant or air, to cool the material quickly. This rapid cooling prevents the re-precipitation of alloying elements and retains them in a solid solution state. Allowed quenching delays (immersion delays) are typically dictated by the type of product or fabrication process and section thickness of the material, and typically ranges from 5s to 15s. In addition, some processes require the material to retain its “as quenched’ properties by preventing the natural aging process to happen after quenching. This is typically done through refrigeration of the material quickly after the quenching phase is complete.
Benefits of Solution Heat Treatment
Improved Ductility: Solution heat treatment typically results in improved ductility of the aluminum alloy. Homogenization: The process helps achieve a more homogeneous distribution of alloying elements throughout the material.
Preparation for Aging: Solution treatment is often a precursor to subsequent aging
processes that impart additional strength and hardness to the alloy.
Commonly Treated Alloys
Aerospace Alloys: Aluminum alloys used in the aerospace industry, such as the 2xxx and 7xxx series, often undergo solution heat treatment.
Wrought Alloys: Certain wrought aluminum alloys, including those from the 6xxx series, are commonly subjected to solution heat treatment.
Importance of Aluminum Solution Heat Treatment Process
In summary, the aluminum solution heat treatment process is a crucial step in optimizing the mechanical properties of aluminum alloys. By dissolving alloying elements and achieving a uniform solid solution, the material becomes more ductile and is better prepared for subsequent process steps and heat treatments, such as aging, to further enhance its strength and hardness.
