Heat Treatment of Aluminum Alloy Extrusion Products
Modern aluminum extrusions are employed in a wide range of aerospace, automotive, industrial and consumer applications, providing efficient and cost-effective solutions to many design challenges. Aluminum extrusions have a range of associated physical and mechanical properties that can be tailored to meet specific design requirements. These properties are heavily influenced by the metalworking and heat treatment process employed in the production of the final extrusion.
Aluminum alloys are typically heat treated in order to alter the physical, mechanical and corrosion properties of the material. Heat treatment of aluminum alloys involves three main stages: homogenization, stress relief, and aging. Homogenization is the process used to homogenize the alloy microstructure, allowing a more uniform distribution of characteristics throughout the entire component. During the homogenization process, an aluminum alloy is heated to an elevated temperature, held for an appropriate period of time to achieve melt-back/solid solution and quenched.
Following homogenization, the component is then typically heat treated with low-temperature thermal stresses to relieve residual stresses due to the metalworking process or welding. This stage of the heat treatment process assists to reduce the possibility of component distortion or cracking. Finally, the component is typically “aged” or “precipitation hardened” to increase the alloy hardness after forming. During this process, the aluminum component is heated to a temperature just below the melting point, and held for a period of time specified by the alloy producer. In this temperature range, most alloy constituents will enter a metastable state, and slowly dissolve into the aluminum alloy matrix during a process referred to as “aging”. The heat treatment process results in an increase in strength and hardness of the component due to the precipitated particles dispersed throughout the alloy microstructure.
In order to optimize component performance, a correct and specific heat treatment schedule is essential, and can be determined based on the alloy grade and intended application. As such, it is important that a Recognized Practitioner (e.g. metallurgist) is consulted when establishing the correct heat treatment schedule.
The heat treatment of aluminum alloys is a process of ensuring the best possible performance from an individual component. It is an important step in the aluminum alloy production process and plays a critical role in determining overall component performance and integrity.
