Aluminum 6463: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 6463 is a member of the 6xxx series of aluminum alloys, which are aluminum–magnesium–silicon alloys recognized primarily for being heat-treatable through precipitation hardening. The 6xxx family balances moderate strength with good formability and surface finish, making members like 6463 attractive for extruded architectural and structural applications.

The principal alloying elements in 6463 are silicon and magnesium, which combine to form Mg2Si precipitates during artificial aging; small controlled amounts of iron, manganese, chromium and titanium appear as residual or deliberate microalloying additions to influence grain structure and processing. Strength is achieved predominantly through solution heat treatment followed by quenching and artificial aging (T5/T6 series), although some properties can be tuned by cold work.

Key traits of 6463 include good extrudability, a fine surface finish suited to anodizing, reasonable strength-to-weight ratio, and corrosion resistance typical of Mg–Si alloys. Weldability is generally good with standard aluminum fusion processes, though the heat-affected zone (HAZ) can soften after welding and must be factored into design.

Typical industries using 6463 include architectural extrusion (window frames, curtain walls), light structural and decorative extrusions, consumer electronics housings where appearance and finish matter, and some lightweight structural components. Engineers choose 6463 when a combination of good extrudability, anodizing quality, and moderate heat-treatable strength is required over higher-strength but less-finishable alternatives.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–35%)	Excellent	Excellent	Fully annealed; best for forming and bending.
H14	Low–Medium	Moderate (10–20%)	Good	Good	Strain-hardened for modest strength increase through cold work.
T5	Medium	Moderate (8–15%)	Good	Good	Cooled from hot working and artificially aged; common for extrusions.
T6	Medium–High	Lower (8–12%)	Good–Fair	Good	Solution heat-treated and artificially aged for near-peak strength.
T651	Medium–High	Lower (8–12%)	Good–Fair	Good	Solution heat-treated, stress relieved by stretching, then artificially aged.

Temper selection controls the trade-off between strength, ductility, and formability. Annealed (O) tempers maximize ductility and are preferred for complex cold forming or bending operations where minimal springback and fracture risk are required.

Heat-treated tempers such as T5/T6 provide substantially higher yield and tensile strength by precipitating Mg2Si phases, which reduces elongation and limits severe forming; these tempers are preferred where strength and dimensional stability are priorities for extruded profiles.

Chemical Composition

Element	% Range	Notes
Si	0.2–0.9	Silicon provides the other half of Mg2Si precipitates; controls extrusion fluidity and strength.
Fe	0.0–0.35	Iron is an impurity that forms intermetallics, affecting surface appearance and ductility.
Mn	0.0–0.15	Manganese refines grain structure and can improve strength slightly without harming extrudability.
Mg	0.4–0.9	Magnesium is the primary strengthening element with silicon; controls precipitation hardening.
Cu	0.0–0.1	Copper is typically low; small amounts can increase strength but reduce corrosion resistance.
Zn	0.0–0.2	Zinc is minimal; higher levels are uncommon in 6463 and are generally undesirable for anodizing.
Cr	0.0–0.1	Chromium helps control grain growth during thermal cycles and improves strength retention.
Ti	0.0–0.15	Titanium is used as a grain refiner during casting and billet production.
Others	Balance (Al) + trace elements	Balance is aluminum; other trace impurities may include Ga, Zr at very low levels depending on supplier.

Silicon and magnesium are the critical combination for heat-treatable strength via Mg2Si precipitation. Secondary elements at low levels are used to tailor grain structure, castability and surface finish. Manufacturers control trace elements to ensure consistent anodizing and to minimize detrimental intermetallics that impair formability and aesthetics.

Mechanical Properties

In annealed condition 6463 exhibits low yield and tensile strength with high elongation, which facilitates extensive forming and bending operations. After solution treatment and artificial aging the alloy manifests a marked increase in yield and tensile strength due to finely dispersed Mg2Si precipitates, but elongation and toughness decline correspondingly. Fatigue resistance follows the general trend of aluminum alloys: improved by surface finish and reduced stress concentrations, and reduced by welding or over-aged conditions in the HAZ.

Hardness correlates with temper and aging response; typical Brinell or Vickers hardness values increase from the O condition to T6 by a sizable margin. Thickness and section size influence achievable properties because cooling rates during quench and aging kinetics vary with mass; thin extrusions reach peak properties more uniformly than thick sections. Temperature and overaging can reduce peak strength, so designers must consider expected service temperature and possible thermal exposure during fabrication.

Property	O/Annealed	Key Temper (T6 / T651)	Notes
Tensile Strength	90–130 MPa	170–250 MPa	Wide ranges depend on section size, exact composition and aging recipe.
Yield Strength	30–60 MPa	120–210 MPa	Yield increases strongly with artificial aging; yield plateau varies by section thickness.
Elongation	20–35%	8–12%	Formability is reduced by aging; design for springback and bend radii accordingly.
Hardness	20–40 HB	50–80 HB	Hardness rise corresponds with precipitation strengthening; measured values depend on scale and method.

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for Al–Mg–Si alloys; used in mass and lightweight design calculations.
Melting Range	~570–640 °C	Onset and range vary with exact composition; avoid prolonged exposure near solidus during fabrication.
Thermal Conductivity	140–180 W/m·K	Lower than pure aluminum but still good for heat-spreading applications; depends on temper.
Electrical Conductivity	~28–38 % IACS	Conductivity is reduced versus pure Al; specific temper and impurity levels affect final value.
Specific Heat	~900 J/kg·K	Approximate value for aluminum alloys at ambient temperatures.
Thermal Expansion	22–24 µm/m·K	Typical coefficient of thermal expansion for 6xxx series alloys.

The physical properties make 6463 suitable for components where weight, thermal management and dimensional control matter. Thermal conductivity and electrical conductivity are lower than pure aluminum but remain advantageous where a combination of formability, finish quality and moderate conductivity are required. Design for thermal expansion and expected operating temperature to avoid thermal stress and dimensional drift.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6 mm	Thin sheets respond well to T5/T6 aging; surface finish critical for anodizing	O, T4, T5, T6	Used for cladding, panels, and decorative elements.
Plate	6–50+ mm	Thicker plates show lower peak strengths due to slower quench rates	O, T6 (limited)	Less common; size limits and slower cooling reduce achievable properties.
Extrusion	Thin to very thick sections	Excellent property tuning via tempers; thin sections achieve higher aged strength	O, T5, T6, T651	Most common form; excellent surface finish for architectural profiles.
Tube	Ø small–large, walls 1–10 mm	Welded or seamless tubes can be aged; wall thickness dictates final properties	O, T5, T6	Common for structural tubing and architectural handrails.
Bar/Rod	Ø 3–50 mm	Bars can be solution treated and aged; machinability typically good	O, T6	Used for machined components and small structural elements.

Extruded profiles are the dominant product form for 6463 because the alloy’s composition and processing produce smooth, anodizable surfaces with good dimensional control. Sheet and plate are used where flatness and panel behavior are required, but thickness and cooling limitations make certain tempers less effective in plate form. Manufacturers typically specify temper and post-processing (stretching, aging) to meet mechanical and surface finish requirements for each product form.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6463	USA	Common designation in aluminum specification sheets and supplier catalogs.
EN AW	6463	Europe	Often listed as EN AW‑6463; chemical constraints and tolerances may vary by EN standard.
JIS	A6063 (approx)	Japan	JIS A6063 is a close comparative alloy in the Mg‑Si family but is not an exact chemical match.
GB/T	6463	China	Chinese standard grades with the same numeric designation exist, but batch tolerances can differ.

Region-to-region standards nominally map 6463 within the Mg–Si family, but subtle differences in impurity limits, mechanical test methods and permitted tempers may exist. When specifying cross-border procurement, verify the actual chemical and temper tolerances on the mill test certificate rather than relying solely on grade numbers. Equivalency is approximate; qualify suppliers to ensure surface finish and mechanical targets are met.

Corrosion Resistance

Atmospheric corrosion resistance of 6463 is comparable to other 6xxx series alloys and is generally good for architectural use when anodized or painted. The alloy naturally forms a protective oxide and performs well in urban and industrial atmospheres, but surface finish and anodizing quality play a large role in long-term behavior.

In marine or high-chloride environments, 6463 resists general corrosion but localized pitting can occur where chloride concentration is high and detergent action is present. The alloy lacks the superior sacrificial properties of higher-magnesium 5xxx alloys, so designers must consider protective coatings, anodizing, or cathodic protection for extended service near seawater.

Stress corrosion cracking (SCC) susceptibility is relatively low for 6xxx alloys compared with high-strength 7xxx alloys, but SCC can still occur under combined tensile stress and corrosive environments, particularly in over-aged or welded conditions. Galvanic interactions with more noble materials (stainless steel, copper) can accelerate localized corrosion of aluminum if electrical continuity and an electrolyte are present; isolation or protective coatings are recommended.

Compared with the 1xxx and 3xxx series, 6463 trades slightly reduced raw conductivity for improved strength and similar atmospheric corrosion resistance. Versus 5xxx alloys, 6463 generally offers better architectural surface finish and anodizing response but less inherent seawater resistance.

Fabrication Properties

Weldability

6463 welds well with common fusion processes such as TIG (GTAW) and MIG (GMAW), and it is suitable for robotic and hand welding on extrusions. Recommended filler alloys include 4043 (Al‑Si) for better fluidity and reduced hot cracking tendency, and 5356 (Al‑Mg) when higher weld strength is desired; select filler based on service environment and post‑weld finishing.

Welding produces an HAZ where precipitate dissolution and re-precipitation can reduce mechanical properties locally, especially in T6 or T651 tempers; designers should account for HAZ softening and consider post-weld heat treatment or mechanical design to avoid overstressing the welded region. Hot cracking is not typically a major problem for 6463 but can arise from poor joint design, contamination, or high restraint; clean surfaces and proper travel speeds mitigate risk.

Machinability

Machinability of 6463 is moderate and comparable to other 6xxx alloys; it machines more easily than many higher-strength heat-treated alloys but not as easily as free‑machining 2xx alloys. Carbide tooling is recommended for production machining; high-speed steels are acceptable for light work. Optimal cutting speeds, feeds and tool geometries depend on temper and hardness; stiff fixturing and chip-breaker geometries improve surface finish and dimensional accuracy.

Chip formation tends to be continuous and ductile; maintain coolant flow to manage built-up edge and surface oxidation. For highly anodized or appearance-critical parts, finish machining and careful control of tool wear are essential to avoid surface defects that anodizing will highlight.

Formability

Formability is excellent in the O and T4 tempers and good in T5/T6 for moderate forming operations typical of extruded profiles. Minimum bend radii depend on temper and thickness; typical recommendations are T/2 to 2T (where T is material thickness) in annealed condition and larger radii for T6 to prevent cracking at the surface.

Cold working increases strength but reduces ductility; designers should sequence forming operations before final artificial aging where possible. Where deep drawing or severe stretch forming is required, select O or T4 tempers and apply proper lubrication and die radii to avoid edge tearing.

Heat Treatment Behavior

As a heat-treatable 6xxx alloy, 6463 responds principally to the solution treatment – quench – age sequence. Typical solution treatment is performed in the 510–540 °C range to dissolve Mg2Si into solid solution, followed by rapid quench to retain a supersaturated solid solution. Artificial aging (T5/T6) then precipitates fine Mg2Si particles to increase yield and tensile strength.

T5 temper is achieved by cooling from hot working and direct artificial aging without a full solution treatment, producing moderate strength gains with good dimensional control for extrusions. T6 (solution treated and artificially aged) provides near-maximum precipitation strengthening. Overaging, or prolonged exposure to elevated temperatures during service or fabrication, coarsens precipitates and reduces peak strength.

T temper transitions are reversible only through re-solution treatment; designers should avoid thermal cycles that unintentionally overage or underage parts intended to meet specific mechanical specifications. For welded components, localized dissolution and re-precipitation in the HAZ may require post-weld thermal treatments to restore uniform properties in critical applications.

High-Temperature Performance

Service temperatures for 6463 are typically limited to the range where precipitate stability is maintained; continuous service above approximately 120–150 °C will progressively reduce yield and tensile strength due to precipitate coarsening. Short excursions to higher temperatures may be tolerated, but dimensional stability and mechanical properties will be affected if aging kinetics proceed.

Oxidation at elevated temperatures is minimal compared with ferrous alloys because aluminum forms a protective oxide, but scale and surface discoloration can occur and compromise anodizing and appearance. In the HAZ of welded components, thermal exposure can cause softening and reduce fatigue life; designs requiring elevated temperature resistance should consider alternate alloys with improved high-temperature stability.

Creep resistance in 6463 is limited for sustained loads at elevated temperatures, so designers should avoid using the alloy for load-bearing parts that operate near the softening temperature for extended periods. For thermal cycling applications, account for reduced fatigue strength and possible microstructural coarsening over time.

Applications

Industry	Example Component	Why 6463 Is Used
Architectural	Window frames, curtain wall extrusions	Excellent extrudability, anodizing surface finish, dimensional control
Automotive	Trim, decorative rails	Good surface finish, moderate strength with weight savings
Aerospace (non-critical)	Interior fittings, fairings	Good strength-to-weight and surface appearance for non-structural parts
Marine	Decorative railings, trim	Corrosion resistance with appropriate coatings and anodizing
Electronics	Enclosures, heat-spreading housings	Good thermal conductivity, aesthetic finish for consumer products

6463 is frequently selected for components where extruded complex cross-sections and high-quality anodized surfaces are required along with moderate heat-treatable strength. The alloy’s balance of finishing quality, mechanical properties in aged tempers, and ease of fabrication has sustained its use in architectural and light structural markets.

Suppliers often deliver extruded profiles in T5 or T6 condition with specified surface treatments, enabling direct installation or secondary machining and finishing as needed.

Selection Insights

Choose 6463 when designs require high-quality extruded surface finish and anodizing combined with moderate heat-treatable strength and good extrudability. The alloy is a logical selection for architectural profiles and decorative structural elements where appearance and dimensional control are priorities.

Compared with commercially pure aluminum (1100), 6463 trades some electrical and thermal conductivity and formability for substantially higher strength when aged, making it preferable where structural stiffness and anodized finish are required. Compared with work-hardened alloys like 3003 or 5052, 6463 generally offers higher achievable strength after aging with similar or slightly reduced corrosion resistance; choose 6463 when post-forming heat treatment or extrusion-based shaping is part of the process.

Against other heat-treatable alloys such as 6061 or 6063, 6463 is selected when superior surface finish for anodizing and extrudability are desired even if peak strength is somewhat lower than 6061; for heavier structural demands where higher strength is required, 6061 may be the preferred alternative. Balance cost and availability with the need for finish quality and extrusion complexity in the selection decision.

Closing Summary

Aluminum alloy 6463 remains a widely used 6xxx series alloy for applications that demand excellent extrudability, anodizing-friendly surface finish and moderate precipitation-strengthened mechanical properties. Its combination of machinability, weldability and predictable heat-treatment behavior makes it a reliable choice for architectural, decorative and light structural components where appearance and dimensional control are as important as strength.