Aluminum A6063: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A6063 is a member of the 6xxx series aluminum alloys, an Al-Mg-Si family that is primarily strengthened by precipitation hardening. Its major alloying elements are silicon and magnesium, which combine to form Mg2Si precipitates during heat treatment; trace additions of iron, copper, chromium, zinc and titanium are controlled to balance strength, extrudability and surface finish.

A6063 is a heat-treatable alloy (precipitation/age hardenable) rather than a pure work-hardening alloy, so it achieves higher strength through solution treatment and artificial or natural aging. Typical traits include moderate-to-good tensile and yield strength, excellent extrudability and surface finish, good corrosion resistance in many atmospheres, and very good anodizing characteristics.

Industries that commonly use A6063 include architectural/structural extrusions (window frames, curtain walls), building and construction, automotive non-structural components, and certain electrical/thermal applications where good surface finish and moderate strength are required. Engineers choose A6063 over other alloys when balanced requirements for extrudability, anodizing appearance, corrosion resistance and cost are prioritized over maximal peak strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (12–18%)	Excellent	Excellent	Fully annealed, best formability and ductility
H14	Low-Moderate	Moderate	Very Good	Very Good	Strain-hardened light, used for extrusions requiring moderate strength
T4	Moderate	Moderate-High	Good	Good	Solution heat-treated and naturally aged, Good formability with some strength
T5	Moderate-High	Moderate	Good	Good	Cooled from hot working and artificially aged, common for extrusions
T6	High	Moderate-Low (8–14%)	Fair	Good	Solution heat-treated and artificially aged to near-peak strength
T651	High	Moderate-Low	Fair	Good	T6 with stress-relief by controlled stretching, common for structural extrusions

Temper selection modifies the balance of ductility, yield and tensile strength; O and H-tempers favor forming operations and bending while T5/T6 give higher static strength for service. T6 and T651 are widely used where dimensional stability and higher yield are required, but they sacrifice some bendability and increase springback compared with annealed tempers.

Chemical Composition

Element	% Range	Notes
Si	0.2–0.6	Primary strengthening constituent with Mg to form Mg2Si precipitates
Fe	≤0.35	Impurity; higher Fe reduces extrudability and surface finish
Mn	≤0.10	Minor, can improve strength marginally
Mg	0.45–0.9	Partner for Si in Mg2Si precipitation; controls peak strength capability
Cu	≤0.1	Small amounts can raise strength but may reduce corrosion resistance
Zn	≤0.1	Kept low to avoid susceptibility to galvanic corrosion
Cr	≤0.05	Controls grain structure and improves toughness at times
Ti	≤0.1	Grain refiner; used at controlled levels to refine microstructure
Others	≤0.15 total	Each ≤0.05 typically; balance Al

The Si-Mg ratio and absolute Mg content primarily determine the precipitation kinetics and the attainable strength after aging. Controlled low levels of Fe, Cu and Zn preserve surface finish and anodizing consistency while Ti and Cr are used in trace amounts to refine grains and reduce hot shortness during processing.

Mechanical Properties

A6063 exhibits a tensile-yield profile that is strongly dependent on temper and section thickness; thin-wall extrusions in T6 can attain useful strengths while retaining good surface finish. Yield strength in annealed conditions is relatively low, permitting large plastic deformations for forming, and after solution treatment plus artificial aging the Mg2Si precipitates provide significantly higher yield and tensile strength. Elongation and ductility decrease with increasing strength; T6 yields higher strengths but lower elongation and greater springback during forming operations.

Hardness tracks the aged condition with annealed alloys registering low Brinell/Knoop values and T6 materials moving into moderate hardness ranges; this affects wear and machining response. Fatigue performance is adequate for non-critical cyclic applications but is sensitive to surface condition, extrusion defects and weld-induced softening in heat-affected zones. Section thickness influences quench response and achievable strength: thicker sections cool more slowly after solution treatment and therefore may not reach full peak hardness without extended aging or modified processing.

Property	O/Annealed	Key Temper (e.g., T6/T651)	Notes
Tensile Strength	~110–155 MPa	~160–230 MPa	Wide range due to section size, temper and aging schedule
Yield Strength	~60–95 MPa	~120–180 MPa	T6/T651 yields commonly reported in 120–160 MPa range for typical extrusions
Elongation	~12–18%	~8–14%	Elongation decreases with higher tempers and thicker sections
Hardness (HB)	~35–50 HB	~60–75 HB	Brinell approximations; depends on ageing and microstructure

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for Al-Mg-Si alloys providing good strength-to-weight
Melting Range	~582–652 °C	Alloying depresses and broadens melting range compared with pure Al
Thermal Conductivity	~160 W/m·K	Good thermal conduction; slightly lower than pure aluminum and 1xxx series
Electrical Conductivity	~30–36 %IACS	Moderate electrical conductivity, reduced from commercially pure aluminum
Specific Heat	~900 J/kg·K	Typical aluminum alloy value used in thermal calculations
Thermal Expansion	~23–24 µm/m·K	Moderate coefficient; important for dimensional stability in thermal cycles

A6063’s thermal and electrical conductivities make it acceptable for some thermal management uses, but it is not as conductive as 1xxx-series alloys. The relatively high thermal expansion coefficient requires attention in assemblies combining dissimilar materials during thermal cycling or where tight tolerances are required.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Moderate; supplier dependent	O, Hxx, T4, T5	Used for light panels and formed components
Plate	>6.0 mm	Lower achievable peak due to quench limitations	O, T4, T6 (limited)	Thicker sections may not reach full T6 properties without special processing
Extrusion	Thin walls to large profiles	Designed for uniform properties in cross-section	T5, T6, T651	A6063 is optimized for extrusion—excellent surface finish and dimensional control
Tube	Various diameters/wall thicknesses	Strength varies with wall thickness and temper	O, T4, T5	Common for architectural and structural applications
Bar/Rod	Small-diameter up to large	Machinability good in O/T4	O, T6	Used for machined components and fabricated parts

Extrusion is the dominant manufacturing route for A6063; the alloy chemistry and thermomechanical processing are tuned to give smooth flow, good die filling and superior surface appearance for anodizing. Sheets and plates are used where flat stock is required, but attention must be paid to thickness-dependent aging and quench sensitivity when targeting high tempers.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A6063	USA	ASTM/AA designation commonly used in North America
EN AW	6063	Europe	EN AW-6063 often specified with additional temper suffixes
JIS	A6063	Japan	JIS recognizes similar Al-Mg-Si compositions with local processing standards
GB/T	6063	China	GB/T 6063 equivalents are commonly used in Chinese specifications

While catalogue numbers appear consistent across regions, specifications can differ in allowable impurity limits, mechanical property testing requirements and standard temper definitions. Engineers should review relevant national standards and supplier mill certificates for details on chemical limits, mechanical testing and process controls before specifying.

Corrosion Resistance

A6063 shows good atmospheric corrosion resistance in urban and rural environments due to the formation of a stable aluminum oxide film and its modest alloying content. Its relatively low copper and iron levels help maintain corrosion resistance, and it anodizes well to produce a durable protective and decorative oxide layer useful in architectural applications.

In marine environments the alloy performs acceptably for many uses, but chloride-rich atmospheres accelerate localized corrosion and pitting, particularly if the anodized coating is compromised. When used in marine or aggressive chloride exposures engineers commonly specify protective finishes, sacrificial anodes, or select alternative alloys with higher magnesium or added corrosion-resistant chemistries.

Stress corrosion cracking (SCC) risk for 6xxx alloys is generally low at ambient temperatures but can increase under sustained tensile loading, elevated humidity and certain temper conditions; T6 tempers may be more susceptible than fully annealed tempers. Galvanic interactions should be managed—A6063 is anodic to many stainless steels but cathodic to magnesium; appropriate isolation, fastener selection and coatings mitigate galvanic corrosion in mixed-metal assemblies.

Fabrication Properties

Weldability

A6063 is readily welded by common fusion processes such as TIG and MIG with predictable behavior, though some softening in the heat-affected zone is expected in aged tempers. Common fillers include ER4043 (Al-Si) for improved fluidity and appearance, or ER5356 (Al-Mg) when higher post-weld strength or corrosion resistance is required; selection depends on the required post-weld properties and anodizing considerations. Hot cracking susceptibility is relatively low, but weld joint design, cleanliness and pre/post-heat treatments influence defect rates and residual stresses.

Machinability

Machinability of A6063 is moderate—better than many 5xxx alloys but not as free-cutting as specialty alloys like 2011. Carbide tooling and rigid setups with appropriate lubricants deliver best tool life; typical machining parameters align with standard aluminum practice (high spindle speed, moderate feed, aggressive chip evacuation). Surface finish and burr control are often excellent owing to the alloy’s ductility, but temper and prior heat treatment influence chip morphology and tool wear.

Formability

A6063 exhibits excellent cold formability in soft tempers (O, Hxx, T4) and can be bent, roll-formed and drawn with tight radii when managed appropriately. As temper increases (T5, T6), springback increases and minimum bend radii grow; specifying T4 or O for forming followed by post-forming aging is a common strategy. Extrusions with complex thin-wall geometry are one of the alloy’s strengths, and die design plus lubrication optimize the formability and surface finish.

Heat Treatment Behavior

A6063 is heat-treatable by solutionizing, quenching and aging to produce precipitate-strengthened conditions; the key strengthening phase is Mg2Si. Typical solution treatment is carried out near 520–545 °C to dissolve soluble phases, followed by rapid quench to retain a supersaturated solid solution; quench rates and section thickness strongly influence final properties. Artificial aging regimes vary: T5-type aging (cooled from hot working then aged) commonly uses ~150–200 °C for several hours, while T6 (solution treated then artificially aged) uses similar temperatures but after solution treatment to achieve higher strength.

Temper transitions are practical tools: components may be extruded in a thermally stabilized condition, formed in T4 or O to maximize ductility, and then artificially aged to achieve required service strength. Overaging reduces strength but can improve toughness and stress corrosion resistance, so aging schedules are selected to balance mechanical properties, dimensional stability and corrosion performance. Special attention is required for thick sections where quench sensitivity can prevent full hardening; in such cases modified aging or design adjustments mitigate property gradients.

High-Temperature Performance

A6063 maintains reasonable mechanical properties up to modest elevated temperatures, but significant reduction in yield and tensile strength occurs above approximately 150–175 °C. Prolonged exposure to temperatures above aging ranges can coarsen strengthening precipitates, leading to softening and loss of dimensional stability; designers should avoid sustained service at temperatures that approach or exceed artificial aging temperatures. Oxidation is minor compared with ferrous alloys, but high-temperature exposure without protective coatings can degrade surface finish and anodized layers.

Heat-affected zones adjacent to welds can experience softening due to overaging or dissolution of precipitates, which reduces local strength; post-weld heat treatment or design accommodations are sometimes required for critical applications. Thermal cycling can exacerbate fatigue and dimensional drift in compressed or constrained assemblies, so accounting for thermal expansion and possible creep at long term elevated temperatures is important for reliable performance.

Applications

Industry	Example Component	Why A6063 Is Used
Architectural/Construction	Window frames, curtain wall extrusions	Excellent extrudability, anodizing finish, and sufficient strength
Automotive	Trim, roof rails, non-structural rails	Good surface finish, corrosion resistance and cost-effective extrusion
Marine	Masts, handrails, trim	Corrosion resistance and anodizing for appearance
Electronics	Enclosures, moderate-performance heat sinks	Thermal conductivity and machinability with good finish
Furniture & Fixtures	Lighting housings, display systems	Cost, formability and surface finishing capability

A6063 is particularly dominant where complex extruded profiles with tight dimensional control and high-quality surface finishes are required. The alloy’s blend of extrudability, reasonable strength and anodizing response keeps it popular for visible architectural components and cost-sensitive fabricated parts.

Selection Insights

A6063 is preferred when high-quality extrusions, excellent surface appearance after anodizing, and moderate strength are main priorities. Choose A6063 over softer 1xxx-series alloys (e.g., 1100) when improved strength is needed but where good formability and conductivity are still desirable; you trade off some electrical/thermal conductivity vs. significant strength gains.

Compared with work-hardened alloys such as 3003 or 5052, A6063 offers higher achievable strength after heat treatment and better anodizing results, while 3xxx/5xxx alloys retain better ductility and sometimes superior corrosion resistance in very aggressive marine environments. Compared with 6061, A6063 commonly provides superior extrudability, smoother surface finish and better anodized appearance, at the expense of lower peak strength, so A6063 is selected for intricate architectural extrusions whereas 6061 is chosen for higher-strength structural or heavily loaded parts.

Select A6063 when design priorities include tight-profile extrusions, decorative finishes, moderate loading and good manufacturability; avoid it when highest strength or maximum electrical conductivity is the primary requirement. Always confirm temper, section thickness and post-processing plans with suppliers to ensure that the delivered product meets design intent.

Closing Summary

A6063 remains a versatile aluminum alloy for modern engineering because it uniquely balances extrudability, anodizing capability, corrosion resistance and moderate strength in a cost-effective package. Its widespread adoption in architectural and fabricated components is driven by predictable processing behavior and the ability to tailor properties through temper and aging to meet diverse application needs.