Aluminum 6063A: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

6063A belongs to the 6xxx series of aluminum alloys, a family characterized by aluminum-magnesium-silicon chemistry optimized for extrusion and moderate strength through precipitation hardening. The principal alloying elements are silicon and magnesium, which combine to form Mg2Si precipitates that provide age-hardening capability when the alloy is heat treated.

6063A is a heat-treatable alloy; strengthening is achieved primarily through solution heat treatment, quenching, and subsequent artificial aging to precipitate fine Mg2Si dispersoids. Key material traits include good extrudability, attractive surface finish after anodizing, reasonable mechanical strength for structural profiles, and superior corrosion resistance compared with many work-hardened series.

Typical industries that use 6063A include architectural systems (window frames, curtain walls, trim), general-purpose structural extrusions, transportation components, and building products where profile complexity and surface quality are critical. Engineers choose 6063A over other alloys when a combination of excellent extrudability, anodizing response, and a balance of strength and formability is required rather than the highest possible strength.

6063A is often selected in preference to firmer 6xxx variants when fine surface finish and extrusion dimensional control are priorities. The alloy yields good weldability and good machinability relative to other extrusion-focused aluminum alloys, enabling economical production of complex profiles that require post-processing such as anodizing or painting.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; maximum ductility for forming
H12	Low-Medium	Moderate	Good	Excellent	Light, non-reversible work hardened; limited forming
H14	Medium	Moderate	Fair	Excellent	Common commercial temper for moderate strength
T1	Medium	Moderate	Good	Excellent	Cooled from hot working and naturally aged
T4	Medium	Moderate	Good	Excellent	Solution heat-treated and naturally aged
T5	Medium-High	Moderate	Fair	Excellent	Cooled from hot working and artificially aged
T6	High	Moderate-Low	Limited	Good	Solution treated, quenched and artificially aged; peak strength
T651	High	Moderate-Low	Limited	Good	Solution treated, stress relieved by stretching, artificially aged
T66	High	Moderate-Low	Limited	Good	Slightly overaged to improve stability against SCC

Temper has a primary control over the balance between strength and ductility in 6063A. Annealed and lightly worked tempers offer the best formability for bending and complex shaping, while T5/T6 and their stabilized variants deliver the highest usable strengths for structural applications.

Chemical Composition

Element	% Range	Notes
Si	0.2–0.6	Silicon combines with Mg to form Mg2Si precipitates; controls extrudability and strength
Fe	≤0.35	Iron is an impurity that diminishes corrosion resistance and can form brittle intermetallics
Mn	≤0.10	Small amounts may improve strength marginally but are usually limited to preserve extrudability
Mg	0.45–0.9	Magnesium participates in precipitation hardening; primary contributor to strength
Cu	≤0.10	Copper is kept low to reduce susceptibility to stress corrosion cracking
Zn	≤0.10	Zinc is limited to avoid hot cracking and maintain anodizing characteristics
Cr	≤0.10	Chromium can control grain structure and reduce recrystallization during processing
Ti	≤0.10	Titanium is used as a grain refiner in castings and billets
Others	≤0.15 total	Other elements (each ≤0.05) can be present as residuals or minor additions

The Si–Mg ratio is the defining chemistry for the 6xxx series; proper balance determines the volume fraction and stability of Mg2Si precipitates, which directly control achievable peak strength and response to aging. Minor elements and impurities influence extrusion behavior, surface finish, anodizing response, and susceptibility to intermetallic formation during melting and solidification.

Mechanical Properties

Tensile behavior of 6063A varies widely with temper and cross-section thickness. In annealed condition the alloy exhibits low yield and tensile strengths but high ductility and elongation, facilitating deep drawing and tight bend radii. In T5/T6 tempers the alloy develops significantly higher tensile and yield strengths from precipitation hardening, with a concomitant reduction in elongation and cold formability.

Yield strength is a function of temper and thermal history; typical yield for common structural tempers lies in the 70–170 MPa range depending on temper and thickness, while ultimate tensile strength typically ranges from ~115 MPa in O condition up to ~215–260 MPa in T6. Hardness tracks strength; annealed material is relatively soft while artificially aged tempers can approach Brinell values that support machining and structural use.

Fatigue performance is generally good for extruded profiles without severe surface defects; fatigue life is sensitive to surface finish, notches, and residual stresses introduced during forming or welding. Thickness and section profile influence mechanical performance: thinner extrusions and sheet attain peak temper strengths more quickly during aging, whereas thicker sections may require extended solution treatment to homogenize and fully develop peak hardness.

Property	O/Annealed	Key Temper (e.g., T6)	Notes
Tensile Strength	~110–160 MPa	~215–260 MPa	Range depends on section thickness and heat treatment uniformity
Yield Strength	~40–90 MPa	~140–170 MPa	Yield increases substantially with artificial aging
Elongation	~20–30%	~6–12%	Ductility reduced in peak-aged conditions
Hardness	~30–40 HB	~60–75 HB	Correlates with precipitation state and dislocation density

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for wrought aluminum alloys; contributes to high specific strength
Melting Range	~582–652 °C	Nominal solidus–liquidus window for Al–Mg–Si compositions; processing must avoid incipient melting
Thermal Conductivity	~150–200 W/m·K	High conductivity useful for heat dissipation; varies with temper and alloying
Electrical Conductivity	~30–45 % IACS	Lower than pure Al due to alloying; acceptable for many electrical components
Specific Heat	~900 J/kg·K	Good heat capacity for thermal buffering in service
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Typical aluminum expansion; relevant for mating with dissimilar materials

6063A combines low density with relatively high thermal and electrical conductivity, making it suitable for heat sinks and architectural components where weight and thermal performance are both considerations. The melting range and solidification behavior require controlled casting and extrusion billets to avoid intermetallic segregation and ensure consistent mechanical properties along extruded lengths.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6 mm	Uniform, can be cold-rolled to H tempers	O, H14, H24	Used for panels, facades, and components requiring surface finish
Plate	6–25 mm	Thicker sections have slower response to heat treatment	O, T6 (limited)	Less common due to extrusion focus; may require extended solution times
Extrusion	Complex cross-sections, 1–100+ mm profiles	Excellent directional properties; strength depends on cooling and aging	T5, T6, T651	Primary market for 6063A; excellent dimensional control and surface finish
Tube	Ø small to large, wall thickness variable	Similar to extrusions; seamless or welded	O, T6	Used for architectural tubing, frames, and structural members
Bar/Rod	Ø 3–50 mm	Solid profiles used for machined parts	O, T6	Common for stock shapes machined into fittings and hardware

Extrusion is the dominant product form for 6063A due to its fine balance of fluidity in the billet and stability in the die, producing long profiles with tight tolerances. Sheets and plates are processed by rolling and may be supplied in annealed or partially hardened tempers; thicker plate is less typical because 6063A is optimized for extrusion rather than heavy-section applications.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6063A	USA	Aluminum Association designation; commonly used in North American specifications
EN AW	6063	Europe	EN AW-6063 (AlMgSi) is the European equivalent; similar chemistry and tempers
JIS	A6063	Japan	JIS A6063 corresponds to similar Al–Mg–Si compositions used in Japanese standards
GB/T	6063	China	GB/T 6063 aligns closely with AA 6063 chemistry and mechanical requirements

Standards across regions are functionally similar but can impose slightly different limits on impurity elements, grain structure, and acceptance testing for extrusions. These subtle regulatory differences can affect supplier qualification and anodizing behavior, so procurement specifications should reference both the alloy designation and the governing standard when cross-sourcing internationally.

Corrosion Resistance

6063A offers good atmospheric corrosion resistance owing to its relatively low copper content and stable anodic film formation, making it suitable for exterior architectural use. The alloy anodizes uniformly, producing attractive and corrosion-resistant oxide layers that are widely used in façade and window-frame markets.

In marine and high-chloride environments, 6063A performs acceptably for many structural applications, though prolonged exposure to splash or spray service can promote pitting on rough or mechanically damaged surfaces. Measures such as protective coatings, proper drainage, and anodizing help mitigate localized corrosion in aggressive environments.

Stress corrosion cracking (SCC) susceptibility is lower in 6063A than in some higher-copper alloys, but can still occur under tensile residual stresses and highly corrosive conditions. Galvanic interactions with more noble metals must be considered; when coupled to steels or copper alloys, 6063A will act anodic and should be electrically insulated or designed with sacrificial anodes where corrosion control is critical.

Compared with 5xxx (Al–Mg) alloys, 6063A generally offers superior anodizing and surface finish but slightly reduced resistance to certain aqueous corrosion modes; compared with 2xxx/7xxx high-strength alloys, 6063A provides much better long-term corrosion performance due to lower copper and zinc contents.

Fabrication Properties

Weldability

6063A welds well with common fusion processes such as TIG and MIG, producing sound joints when appropriate filler alloys (commonly 4043 or 5356 depending on joint requirements) are selected. Hot-cracking risks are modest for 6063A but attention to joint design and minimizing weld pool contamination is important to preserve surface appearance. Heat affected zones (HAZ) will experience partial softening in aged tempers; designers should account for reduced local strength and plan post-weld heat treatment or overmatching fillers when required.

Machinability

Machinability of 6063A is moderate to good; it machines easier than many high-strength 6xxx variants because of its balanced hardness and ductility in common tempers. Carbide tooling provides long tool life at typical cutting speeds, and chip control is generally manageable if feeds are optimized for section thickness and temper. Synthetic or soluble cutting fluids help maintain surface finishes and reduce built-up edge when machining anodized or visually critical components.

Formability

Formability is excellent in annealed (O) and lightly worked tempers, allowing tight bend radii and complex forming operations; springback is predictable in extruded sections and can be compensated in die design. Cold-worked and peak-aged tempers reduce formability and increase the risk of cracking during bending; for formed and then heat treated parts, selecting T4 or solution-treating after forming is a common production strategy.

Heat Treatment Behavior

6063A is a heat-treatable alloy principally strengthened by the precipitation of Mg2Si. Solution treatment typically involves heating to approximately 520–560 °C to dissolve soluble constituents, followed by rapid quenching to retain a supersaturated solid solution. Artificial aging (T5/T6) follows quenching or controlled cooling and is performed at temperatures commonly between 160–200 °C for times tuned to reach desired strength and dimensional stability.

T temper transitions include T4 (solution-treated and naturally aged), T5 (cooled from hot working and artificially aged), and T6 (solution-treated, quenched, and artificially aged). Variants such as T651 add a stress-relief stretch to minimize residual distortion. Overaging (T7/T66) trades some strength for improved stability and resistance to stress corrosion cracking, and is used when in-service thermal exposure or dimensional stability is a concern.

Non-heat-treatable strengthening is limited; light H-series tempers use mechanical work to raise strength but do not achieve the levels available by precipitation hardening. Full anneal (O) is used where maximum ductility and formability are required prior to subsequent operations.

High-Temperature Performance

Service temperatures for 6063A are limited by loss of precipitate strengthening and accelerated diffusion; useful strength is generally maintained up to approximately 100–150 °C, but significant softening occurs at higher sustained temperatures. Creep resistance is modest; for applications with continuous elevated temperatures, designers typically select alloys with higher temperature capability or apply design margins.

Oxidation in air is not severe because aluminum forms a protective oxide, but elevated temperature exposure can alter the surface finish and degrade anodized layers. Heat affected zones adjacent to welds can experience precipitate coarsening and reduced mechanical properties if exposed to elevated post-weld temperatures. For components subjected to intermittent heating, consideration of overaged tempers can improve dimensional stability at the expense of peak strength.

Applications

Industry	Example Component	Why 6063A Is Used
Architectural	Window frames, curtain wall profiles	Excellent extrudability, anodizing, surface finish
Construction	Door frames, handrails, trim	Good corrosion resistance and formability for complex shapes
Transportation	Light vehicle trim, interior structural profiles	Favorable strength-to-weight and good surface appearance
Marine	Non-structural deck fittings, trim	Corrosion resistance and ability to anodize for aesthetics
Electronics	Heat sinks, enclosures	Thermal conductivity and ease of extrusion for fins
Consumer Products	Furniture frames, sporting goods	Combination of formability, finish, and cost effectiveness

6063A is particularly dominant where long, complex extruded profiles with high-quality surface finishes are required, especially when post-process anodizing or painting is part of the product specification. The alloy’s balance of mechanical, thermal, and surface properties makes it a cost-effective choice across many non-extreme structural uses.

Selection Insights

Choose 6063A when extrusion complexity, surface finish (anodizing), and moderate structural strength are the primary drivers of design. If maximum strength is required, stronger 6xxx or 7xxx alloys may be better, but they often compromise anodizability and surface quality.

Compared with commercially pure aluminum (1100), 6063A trades higher strength and better extrudability at the cost of somewhat lower electrical conductivity and slightly reduced formability; 1100 may be chosen when electrical conductivity or maximum ductility is paramount. Versus work-hardened alloys such as 3003 or 5052, 6063A provides higher age-hardenable strength and superior anodizing/appearance but can be less robust in certain corrosive chloride environments. Compared with 6061, 6063A is preferred when extrusion surface quality and finer detail are required despite lower peak strength; 6061 would be selected where higher structural strength and fracture toughness are priorities.

Consider availability, cost, and finishing requirements in the selection decision: 6063A is commonly stocked for extrusions and architectural profiles, which can reduce lead times and processing costs compared with less-common alloys.

Closing Summary

6063A remains a widely used aluminum alloy because it combines excellent extrudability, good anodizing response, and a useful balance of strength and formability for architectural and structural profiles. Its versatility across fabrication routes and predictable heat-treatment behavior make it a practical choice for designers seeking reliable performance and attractive surface finishes in medium-strength aluminum applications.