Aluminum alloys are grouped into a four-digit system based on their primary elemental additions, with the 6xxx series defined by magnesium and silicon. The specific alloy 6063 is one of the most widely used in this group, valued for its balance of strength, formability, and finish quality. Because of its superior performance in visible, exposed environments, 6063 aluminum has earned the common nickname of “Architectural Aluminum.”
Composition and Classification
The classification of 6063 aluminum as a member of the 6xxx series is determined by magnesium (Mg) and silicon (Si) as its principal alloying elements. Magnesium is typically present in a range of 0.45% to 0.9%, while silicon is found between 0.2% and 0.6% by weight. This combination forms the intermetallic compound Mg2Si.
The formation of the Mg2Si compound makes the alloy heat-treatable, allowing its mechanical properties to be enhanced through thermal processing. This precise chemical composition distinguishes 6063 from other similar alloys like 6061, which contains higher percentages of alloying elements for increased strength. Iron content is kept deliberately low, typically less than 0.35%, which contributes to the superior surface finish the material is known for.
Key Physical Properties
The physical properties of 6063 aluminum are tailored for non-structural, high-visibility applications, prioritizing surface aesthetics and environmental stability. The alloy is characterized by its moderate strength, which is sufficient for many architectural components but lower than the higher strength 6061 alloy. In a common T6 temper, 6063 possesses an ultimate tensile strength of at least 28,000 psi and a yield strength of about 23,000 psi.
A primary attribute of 6063 is its exceptional surface finish quality, resulting from its clean chemical composition and high extrudability. This smoothness makes it an ideal substrate for various decorative treatments. The alloy exhibits high corrosion resistance, a natural feature of the 6xxx series, enhanced by the lack of copper compared to 6061. This resistance allows it to be used outdoors without protective coatings.
The material is highly receptive to anodizing, a process that electrochemically thickens the naturally occurring oxide layer on the aluminum surface. This process creates a hard, durable, and porous film that readily accepts dyes, offering excellent color retention and additional protection against weathering and abrasion. The ability to achieve a fine, aesthetically pleasing finish after anodizing is a major reason for its popularity.
Processing and Heat Treatment
The manufacturing of 6063 is dominated by the extrusion process. Its chemical balance grants it excellent extrudability, meaning it can be easily pushed through a die to form complex, intricate cross-sections with thin walls. This makes it the preferred material for creating custom profiles for window frames and specialized trim pieces.
After extrusion, the material’s final mechanical properties are set through specific heat treatments, designated by a “T” temper code. The two most common tempers for 6063 are T5 and T6, which affect the material’s final strength and hardness. The T5 temper involves cooling the material from the high temperature of the extrusion press and then artificially aging it to a stable condition. This process, often called air-quenching, utilizes the residual heat from manufacturing.
The T6 temper requires a full solution heat treatment followed by a rapid water-quenching step and then artificial aging. This intensive process maximizes the precipitation of the strengthening Mg2Si particles, resulting in a material that is approximately 20% to 25% stronger than the T5 temper. The choice between T5 and T6 depends on the application, with T5 offering better formability and lower cost, and T6 providing higher strength for load-bearing requirements.
Primary Applications
The unique combination of excellent surface finish, high corrosion resistance, and superior extrudability makes 6063 aluminum the material of choice for architectural and decorative applications. It is widely used for creating custom window and door frames, where its ability to form complex, weather-tight profiles is highly valued. The material’s corrosion resistance ensures long-term performance in outdoor environments.
Beyond facades, 6063 is frequently employed in railing systems, decorative trim, and shop fittings where a clean, finished appearance is necessary. Its suitability for anodizing is leveraged to produce various colored and textured components for visual integration into building designs. The alloy is also used for utility items such as irrigation tubing and various types of lightweight furniture.