Aluminum 6260: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

6260 is a member of the 6xxx series of aluminum alloys, a family defined by magnesium and silicon as the principal alloying elements that form Mg2Si precipitates. It is a heat-treatable, precipitation-hardenable alloy designed to balance moderate-to-high strength with good extrudability and surface finish, placing it among alloys optimized for structural extrusions and engineered profile work.

Major alloying elements in 6260 are silicon and magnesium, with controlled additions of copper, chromium, manganese and trace titanium to refine grain structure and influence hardening kinetics. The strengthening mechanism is classical age hardening: solution treatment and quench followed by artificial (or natural) aging to precipitate Mg2Si and secondary phases that raise yield and tensile strength.

Key traits of 6260 include a favorable strength-to-weight ratio, good corrosion resistance in atmospheric and mildly marine environments, good welding performance with appropriate filler selection, and reasonable formability in softened tempers. Typical industries include transportation (automotive and rail), architectural and building systems, electrical enclosures and heat-dissipating components where extrudable complex shapes are required.

Engineers select 6260 when they need an extrusion-friendly 6xxx alloy with slightly higher as-extruded strength and improved dimensional stability compared with more common alloys such as 6063. It is chosen over higher-strength 2xxx/7xxx alloys when weldability, surface finish and corrosion resistance are more important than absolute peak strength, and over soft 1xxx or 3xxx alloys when higher structural capacity is required.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for maximum ductility and formability
H14	Low–Medium	Medium	Good	Good	Cold-worked, some increase in yield; limited recovery allowed
T4	Medium	Medium–High	Good	Good	Solution heat-treated and naturally aged; good balance for forming then aging
T5	Medium–High	Medium	Good	Good	Cooled from hot working and artificially aged; commonly used for extrusions
T6	High	Medium–Low	Fair	Fair–Good	Solution treated, quenched and artificially aged for peak strength
T651	High (stable)	Medium–Low	Fair	Fair–Good	T6 with stress-relief by stretching; widely used for extruded structural parts

The temper has a primary influence on the microstructure: soft tempers allow extensive cold forming and bending without cracking, while T6/T651 peak-aged tempers maximize strength at the expense of formability. Weldability and susceptibility to HAZ softening are closely related to temper; T6 parts will show local soft zones after welding unless post-weld heat treatment or appropriate filler alloys are used.

Chemical Composition

Element	% Range	Notes
Si	0.4–0.9	Silicon combines with Mg to form Mg2Si precipitates for strengthening; controls fluidity in casting/extrusion
Fe	0.2–0.5	Iron is an unavoidable impurity; forms intermetallics that can affect toughness and surface finish
Mn	0.05–0.25	Small amounts refine grain and improve strength; high Mn levels not typical for 6260
Mg	0.6–1.0	Primary strengthening element together with Si; controls precipitation kinetics and peak-age strength
Cu	0.05–0.30	Minor Cu increases strength and hardness but can reduce corrosion resistance if excessive
Zn	≤0.2	Zinc typically low; excessive Zn not desirable in this family due to solute interactions
Cr	0.05–0.25	Chromium reduces grain growth and improves temper stability and toughness during heat treatment
Ti	≤0.10	Titanium used as grain refiner in cast or billet production; small additions improve as-extruded surface quality
Others (each)	≤0.05	Trace elements and residuals; Al balance (~remainder)

The composition is deliberately tuned to promote controlled Mg2Si precipitation during artificial aging while limiting deleterious intermetallic phases. Small Cu and Cr additions provide a further lever to adjust strength, HAZ behavior and stress relaxation without severely compromising corrosion resistance.

Mechanical Properties

6260 displays a broad mechanical property envelope that depends strongly on temper, section thickness and processing route. In annealed (O) condition it behaves with high ductility and lower yield and ultimate strengths, suitable for bending and forming operations. After solution treatment and artificial aging (T6/T651), peak tensile and yield strengths are achieved through a fine dispersion of Mg2Si precipitates; ductility decreases accordingly and elongation values drop to the mid-single-digit to low-double-digit percent range.

Hardness follows the same pattern: low Brinell numbers in O condition increase substantially on aging. Fatigue performance in extruded profiles is generally good for this class of alloy but is sensitive to surface condition, machining marks and notches; shot-peening or surface finishing can significantly improve high-cycle fatigue life. Thickness and cross-section shape affect quench rates during solution treatment and therefore peak achievable hardness and strength; thin sections typically reach higher age-hardening response than thick sections.

Property	O/Annealed	Key Temper (e.g., T6/T651)	Notes
Tensile Strength (UTS)	~100–150 MPa	~300–340 MPa	UTS varies with temper and section size; T6 values depend on aging parameters
Yield Strength (0.2% offset)	~35–80 MPa	~240–300 MPa	Yield rise in T6 is significant; T651 provides improved dimensional stability
Elongation (A%)	~20–30%	~8–14%	Elongation drops with increasing temper hardness; measured on standard specimens
Hardness (HB)	~25–40 HB	~70–100 HB	Brinell hardness range indicative; surface condition and temper method affect readings

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical of most Al-Mg-Si alloys; important for strength-to-weight calculations
Melting Range	~570–640 °C	Alloy melting range depends on composition and impurities; solidus–liquidus spread
Thermal Conductivity	~150–170 W/m·K	Good thermal conduction for heat-sinking and thermal management applications
Electrical Conductivity	~30–45 % IACS	Lower than pure aluminum due to alloying; trade-off between conductivity and strength
Specific Heat	~900 J/kg·K	Typical specific heat near room temperature for aluminum alloys
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Coefficient of thermal expansion similar to other 6xxx alloys; important for mating dissimilar materials

Physical properties make 6260 attractive where high stiffness per mass and thermal conduction are required alongside reasonable electrical conductivity. Designers must account for thermal expansion when mating 6260 components to other metals or composites to avoid fatigue from differential thermal cycling.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6 mm	Strength varies with temper; thinner gauges age-harden more uniformly	O, T4, T5, T6	Used for panels, covers and formed components; excellent surface finish for painting/anodizing
Plate	6–50 mm	Thicker sections show reduced age response and slower quench rates	O, T6 (limited)	Heavy sections require controlled quench/aging to avoid soft core regions
Extrusion	Complex profiles, up to several meters long	As-extruded strength (T5) good; T6 available after full heat treatment	T5, T6, T651	Most common form for 6260; cross-section design impacts mechanical anisotropy
Tube	OD 6–200 mm, wall dependent	Welded/seamless tubes show typical 6xxx responses	O, T5, T6	Used for structural tubing, rails and conduits
Bar/Rod	Diameters up to 200 mm	Solid sections have lower age-hardened strength vs thin sections	O, T6	Used for machined fittings and connectors requiring stable dimensions

Processing route determines achievable microstructure: extrusion gives oriented grain flow and surface quality, while plate/plate production and subsequent heat treatments must be optimized for section thickness. Extrusion-specific tempers (T5/T651) are optimized to minimize distortion and provide stable mechanical properties with good surface appearance.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6260	USA	Recognized in American Aluminum Association listings; specific product specs vary by supplier
EN AW	6260	Europe	EN-AW 6260 commonly used in European catalogs; composition and tempers harmonized with ISO standards
JIS	A6260 (approx)	Japan	Japanese standards may list a close composition under A6260 or similar designation; verify with supplier
GB/T	6260	China	Chinese GB/T system has matching entries for many 6xxx alloys; check national spec for tolerance differences

Direct equivalents are generally close but not always identical; regional standards can permit different impurity limits, mechanical property acceptance criteria and allowable tempers. Engineers should always review the specific supplier mill certificate and standard revision when substituting between regional grades for critical applications.

Corrosion Resistance

6260 provides good atmospheric corrosion resistance typical of the 6xxx series, owing to the formation of a stable Al2O3 passive film and the absence of high copper levels that promote galvanic sensitivity. In industrial and urban atmospheres it performs well, and anodizing further improves surface protection and appearance for architectural uses.

In marine or chloride-rich environments, 6260 resists general corrosion reasonably but is susceptible to localized pitting and crevice corrosion if protective coatings are damaged. Compared to marine-specific 5xxx alloys, 6260 has lower innate resistance to seawater; for immersed, long-term marine service aluminum-magnesium alloys with higher Mg content may be preferred.

Stress corrosion cracking susceptibility in 6260 is lower than in high-strength 2xxx and certain 7xxx alloys, but temper and residual stresses are important: overaged tempers show improved SCC resistance, while high-strength peak-aged conditions can be more vulnerable. Galvanic interactions follow normal aluminum behavior: pair 6260 with less noble metals cautiously and insulate contact areas to minimize galvanic corrosion.

Fabrication Properties

Weldability

6260 is readily welded by common methods (GMAW/MIG, GTAW/TIG, and resistance techniques) with good results when using appropriate fillers and pre/post-weld practices. Typical filler alloys are Al-Si (ER4043) or Al-Mg-Si (ER5356) depending on mechanical and corrosion trade-offs; ER4043 reduces hot-cracking risk and improves flow, while ER5356 can preserve higher strength and ductility. Expect HAZ softening near welds in T6 materials; post-weld aging or selecting overmatched filler and T4→T6 post-treatment strategies can mitigate strength loss.

Machinability

Machinability of 6260 is moderate and comparable to other 6xxx alloys; it is not a free-cutting alloy but responds well to carbide tooling and modern CNC practices. Recommended tooling includes TiN-coated carbide inserts with positive rake geometry and good coolant application. Cutting speeds and feeds should be selected to minimize built-up edge; operations like deep drilling and heavy shoulder milling benefit from pecking cycles and rigid fixturing.

Formability

Formability is excellent in O and T4 tempers and degrades as age-hardening increases toward T6. For sheet bending, a conservative minimum inside bend radius is typically 2–3× material thickness for T4 and 3–5× thickness for T6, depending on section geometry and tooling. Cold working (H-series) provides increased yield but reduced elongation; warm forming and appropriate anneal cycles can be used to restore ductility prior to final aging.

Heat Treatment Behavior

6260 is heat-treatable and follows classical precipitation-hardening paths. Typical solution treatment is performed at roughly 520–540 °C for a time adjusted to section thickness to dissolve Mg2Si fully, followed by rapid quenching (water quench) to retain a supersaturated solid solution. Artificial aging is commonly carried out between 150–185 °C for times from a few hours to several hours to achieve T5 or T6 conditions, depending on desired strength-stability trade-offs.

The T4 condition (solution-treated and naturally aged) provides improved formability with later artificial aging possible; T5 is direct aging from the as-extruded condition, offering good dimensional control for long profiles. T651 denotes T6 with a stress-relief stretch to minimize residual stresses and distortion. Non-heat-treatable strengthening must rely on cold work (H tempers) and annealing cycles to tailor ductility.

High-Temperature Performance

6260 begins to lose appreciable strength as temperatures climb above typical artificial-aging ranges; service temperatures above ~120–150 °C progressively dissolve strengthening precipitates and reduce yield and tensile strength. Long-term exposure at elevated temperature leads to overaging and softening, so design must limit sustained operating temperatures or accept reduced load capacity.

Oxidation at elevated temperatures is minimal for short-term exposures due to rapid formation of Al2O3, but the protective layer can be compromised mechanically or chemically. In welded components, HAZ regions are particularly vulnerable to thermal exposure because precipitate distributions were already altered by welding heat cycles, accelerating strength loss under high-temperature service.

Applications

Industry	Example Component	Why 6260 Is Used
Automotive	Extruded structural rails, trim profiles	Good balance of extrudability, strength and surface finish for visible/structural parts
Marine	Architectural superstructure profiles, deck fittings	Corrosion resistance and anodizing capability for non-submerged marine components
Aerospace	Secondary structural fittings and brackets	Favorable strength-to-weight and stable extruded profiles with good machinability
Electronics	Chassis and heat-sink extrusions	Thermal conductivity and ability to form complex extruded shapes with fine surface finish

6260 is particularly effective where extruded geometry, aesthetic surface finish, corrosion resistance and moderate-to-high mechanical properties are required simultaneously. Its role is often as a “workhorse” alloy for engineered profiles where 6063 is marginally weak and 6061 offers similar strength but different extrudability and finish characteristics.

Selection Insights

For engineers choosing a material, 6260 sits between softer alloys and the higher-strength heat-treatable series: it offers stronger as-extruded or peak-aged properties than commercially pure aluminum (1100) while retaining much of the formability and conductivity advantage. When compared with 1100, 6260 trades some electrical and thermal conductivity and formability for significant gains in yield and UTS.

Compared with work-hardened alloys such as 3003 or 5052, 6260 delivers higher age-hardened strength while maintaining comparable corrosion resistance in many atmospheres; however, 3xxx/5xxx alloys may outperform 6260 in long-term immersion or severe marine environments. Versus common heat-treatable alloys like 6061 and 6063, 6260 is often selected for better extrudability or surface finish and slightly different age-hardening response; it is preferred when a specific extrusion performance or dimensional stability (T651) is required even if peak strength is similar or marginally lower.

Use selection logic focused on required forming steps, post-weld treatments, surface finish (anodizing), and service environment. Choose 6260 when you need an extrusion-optimized 6xxx alloy with balanced mechanical properties, good corrosion behavior and reliable weldability, and confirm supplier mill certs for tight-tolerance structural applications.

Closing Summary

6260 remains a relevant engineering aluminum alloy due to its combination of extrusion-friendly processing, controlled precipitation-hardening response, and balanced mechanical and corrosion properties. It fills a practical niche for structural profiles and components where surface finish, weldability and dimensional stability are as important as strength, making it a durable choice for transportation, architectural and industrial applications.