Aluminum EN AW-6061: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

EN AW-6061 is a member of the 6xxx series of aluminum alloys, an Al-Mg-Si class that is widely used for structural applications. The alloy is primarily alloyed with magnesium and silicon which form Mg2Si precipitates; minor additions of copper, chromium and others are used to refine properties. Its strengthening mechanism is heat treatable precipitation hardening, with marked property changes between solution-treated, naturally aged, and artificially aged tempers. Key traits include a favorable balance of strength, corrosion resistance, weldability and reasonable formability, making it a versatile general-purpose alloy.

Typical industries that rely on EN AW-6061 span automotive, aerospace (secondary structures and fittings), marine, electronics (heat sinks and housings) and general fabrication and extrusion markets. The alloy is chosen over 1xxx and 3xxx series primarily for its higher strength and better mechanical performance while retaining good corrosion resistance and weldability. Compared with high-strength 2xxx and 7xxx series alloys, 6061 offers superior corrosion behavior and easier fabrication at moderate strength levels. Designers often pick 6061 when a combination of machinability, weldability and a predictable T6 temper performance is required.

EN AW-6061 is also selected for its wide availability in wrought product forms and consistent property specification across standards, which simplifies supply chain and qualification for production parts. The alloy’s response to standard heat treatments (T4/T6/T651) enables engineers to tailor properties through established thermal processing pathways. Its rating as a structural alloy with a clear pathway to enhanced mechanical behavior by aging makes it a first-choice material for many mid-strength structural components. The balance of cost, availability and multi-process compatibility explains its enduring popularity.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for maximum ductility
H14	Low-Mid	Medium-High	Good	Excellent	Strain-hardened and partially stabilized for moderate strength
T4	Mid	Medium-High	Good	Excellent	Solution heat-treated and naturally aged; good formability
T5	Mid-High	Medium	Fair	Excellent	Artificially aged after cooling from hot work
T6	High	Medium	Fair-Poor	Good	Solution treated and artificially aged to peak strength
T651	High	Medium	Fair-Poor	Good	T6 with stress-relief by controlled stretching to reduce distortion
H116 / H32	Mid-High	Medium	Good	Excellent	Supplier-specific tempers for marine applications and controlled properties

Temper selection controls the microstructure and therefore the macroscopic trade-off between strength and ductility. Annealed O material provides excellent forming and deep drawing capability but has much lower strength than T6; T4 and T5 offer intermediate routes where formability or dimensional control are more important than absolute peak strength. The T6/T651 tempers are widely specified when machining and structural strength are priorities, with the T651 variant used to minimize residual stress and distortion in precision parts.

Chemical Composition

Element	% Range	Notes
Si	0.4–0.8	Silicon combines with Mg to form Mg2Si precipitates; controls strength and extrusion characteristics
Fe	≤0.7	Impurity element; forms brittle intermetallics and affects surface finish and corrosion behavior
Mn	≤0.15	Minor addition; can refine grain size but present only in small amounts in 6061
Mg	0.8–1.2	Primary strengthening element in combination with Si; critical for precipitation hardening
Cu	0.15–0.40	Small Cu increases strength but can reduce corrosion resistance and weldability if excessive
Zn	≤0.25	Low levels; minimal effect but controlled to avoid adverse phases
Cr	0.04–0.35	Controls grain structure and mitigates recrystallization during processing
Ti	≤0.15	Used as a grain refiner in some cast or wrought variants
Others (each)	≤0.05	Trace elements and remainder Al (~balance) dictate toughness and manufacturing behavior

The Mg and Si balance is the defining chemistry for 6xxx series alloys because Mg2Si precipitates provide the principal age-hardening response. Copper and iron are controlled to limit negative effects on corrosion and weldability while chromium and titanium are used in small amounts to control grain structure and recrystallization. The remainder aluminum matrix and low impurity levels keep the alloy conductive and formable relative to higher-alloyed structural steels.

Mechanical Properties

EN AW-6061 exhibits a pronounced range of tensile and yield properties depending on temper, thickness and processing history. In peak-aged T6 condition the alloy shows robust tensile and yield strengths suitable for structural components while retaining moderate ductility; fatigue behavior is reasonable but highly dependent on surface finish and stress concentration. In annealed and T4 conditions the tensile strength is lower and elongation is higher, which favors forming operations and minimizes cracking risk during cold work.

Yield-to-tensile ratio for 6061 typically sits in the 0.7–0.85 range in T6, indicating relatively high yield retention compared with some heat-treatable aluminium alloys. Hardness tracks aging and temper closely; peak-aged T6 hardness values are commonly specified for design and wear considerations. Fatigue resistance is sensitive to microstructural features and the HAZ in welded structures; appropriate surface treatments and stress relief can markedly improve endurance.

Property	O/Annealed	Key Temper (T6)	Notes
Tensile Strength	110–180 MPa	~290 MPa	T6 peak-aged tensile around 260–310 MPa depending on temper and thickness
Yield Strength	35–110 MPa	~240 MPa	Yield varies strongly with temper; T6 yields typically 240–260 MPa in standard product forms
Elongation	15–25%	8–12%	Elongation decreases with increasing strength and thickness; thicker sections tend to show lower ductility
Hardness	40–70 HB	90–110 HB	Brinell hardness indicative of temper; hardness correlates with aging and microstructure

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for wrought aluminium alloys; enables high specific strength
Melting Range	~582–652 °C	Alloy melting range lower than pure Al onset; solidus and liquidus vary with composition
Thermal Conductivity	~150 W/m·K	Good thermal conduction compared with steels; useful for heat sink and thermal spreader designs
Electrical Conductivity	~30–45% IACS	Lower than pure aluminium due to alloying; acceptable for many electrical housings and conductors
Specific Heat	~0.90 J/g·K	High specific heat compared with metals like steel; beneficial for thermal buffering
Thermal Expansion	~23.5 ×10^-6 /K	Coefficient of thermal expansion typical of aluminium alloys and important for fit and thermal cycling design

The combination of low density, good thermal conductivity and moderate electrical conductivity make EN AW-6061 well-suited for lightweight thermal management components and housings. Thermal expansion and relatively high specific heat must be considered where tight dimensional tolerances and thermal cycling occur, particularly in assemblies combining dissimilar materials. Designers should account for conductivity reductions when selecting 6061 for electrical applications compared with high-purity aluminium grades.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6 mm	Consistent across thickness; thinner gauges more susceptible to cold work	O, H14, T4, T6	Widely used for panels and housings
Plate	6–200 mm	May exhibit reduced strength in thick sections due to slower cooling	T6, T651	Structural members and machined parts require careful heat treatment
Extrusion	Complex cross-sections, up to several meters	Strength controlled by temper post-extrusion	T5, T6, T651	Excellent for frames, rails, and architectural profiles
Tube	Diameters from <10 mm to >300 mm	Wall thickness affects temper response	T6, T4	Used for structural, hydraulic and marine tubing
Bar/Rod	Diameter/width variable	Often supplied T6 for machining	T6, T651	Common starting stock for fasteners, shafts and turned components

Sheet and plate are processed with rolling and are often heat-treated after forming to achieve target tempers; extrusions are typically solution-treated or artificially aged following profile formation. Plate and thick sections require special attention to solution treatment and quench rates to achieve uniform properties through the cross-section. Bar and rod stock are commonly supplied in T6 or T651 to allow direct machining to final dimensions with known residual stress and minimal distortion.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6061	USA	Aluminum Association designation commonly used in North America
EN AW	6061	Europe	EN AW-6061 reference per EN standards; nominally the same chemistry and tempers
JIS	A6061	Japan	JIS uses A6061 as a common designation for equivalent wrought alloy
GB/T	6061	China	Chinese standards reference 6061-based alloys with similar chemistry and tempers

Standards across regions specify similar chemistries and temper definitions, but small manufacturing and testing differences can create distinctions in guaranteed mechanical properties and permissible impurity levels. Specifying the standard and temper (for example EN AW-6061 T6 vs. ASTM B209 6061-T6) in procurement documents ensures consistent acceptance criteria for mechanical tests, heat treatment history and dimensional tolerances. Where critical, request mill certificates and process records to verify exact compliance with the target standard.

Corrosion Resistance

EN AW-6061 offers good atmospheric corrosion resistance in most environments, forming a protective oxide that slows general attack. It performs well in mildly corrosive environments and has acceptable resistance for many outdoor applications without special coatings. In marine and chloride-containing environments its resistance is reasonable but inferior to some 5xxx series alloys (e.g., 5083/5052) which are intrinsically more resistant to pitting and exfoliation in seawater.

Stress corrosion cracking (SCC) susceptibility is moderate for 6061; components under tensile stress in aggressive chloride environments can be at risk, especially if heat-treated and not properly stress-relieved. Galvanic interactions with more noble materials (stainless steel, copper) can accelerate localized corrosion; insulating materials and careful fastener selection mitigate galvanic couples. Compared with high-strength Al-Cu alloys (2xxx series) 6061 provides better corrosion behavior but at a cost of lower peak strength, while compared to 3xxx series it trades some formability and conductivity for higher structural capability.

Fabrication Properties

Weldability

EN AW-6061 is readily weldable by common fusion processes such as TIG and MIG, and responds well to filler alloys like ER4043 (Al-Si) and ER5356 (Al-Mg) depending on desired properties. Fusion welding will produce a softened heat-affected zone (HAZ) relative to T6 parent metal, because precipitation hardening constituents dissolve and the HAZ ages differently, so post-weld heat treatment or use of T4/T5 controls may be required. Hot-cracking risk is low compared with some Al-Mg and Al-Cu alloys, but proper joint design and fit-up are important to minimize distortion and porosity. For critical applications, filler choice, preheat, and controlled cooling should be specified to balance corrosion and strength requirements.

Machinability

6061 is regarded as a good machinability alloy among non-free-machining aluminum grades; it machines cleanly with conventional carbide and HSS tooling while producing long, continuous chips if not interrupted. Recommended cutting speeds and feed rates are relatively high compared with steels due to aluminum’s thermal conductivity and low strength; carbide tools with TiN/TiAlN coatings extend tool life in high-speed operations. Surface finish and dimensional stability after machining benefit from starting in T6/T651 tempers, but note that residual stresses may produce springback if not stress-relieved.

Formability

Forming performance is strongly temper-dependent: O and T4 tempers accommodate deep drawing and tight radius bending far better than T6. Typical minimum inside bend radii for 6061-O can be as low as 0.5–1× material thickness for thin gauges, whereas T6 frequently requires 1–3× thickness depending on bend method and tooling. Cold working increases strength but reduces ductility; designers should select softer tempers or plan for solution treatment and re-aging when complex forming is required. For extrusion and profile forming, control of temper and thermal treatment post-forming is essential to maintain dimensional tolerances.

Heat Treatment Behavior

EN AW-6061 is a heat-treatable alloy whose mechanical properties are controlled primarily by the precipitation of Mg2Si particles. Solution treatment is typically performed around 520–550 °C to dissolve precipitate-forming elements into a supersaturated solid solution, followed by rapid quenching to retain these solutes. Subsequent artificial aging at approximately 160–190 °C for durations ranging from several hours to a day precipitates fine Mg2Si dispersoids that strengthen the matrix to T6 conditions.

Different temper paths yield distinct property sets: T4 (solution treated and naturally aged) provides improved formability and reduces cracking in subsequent operations, while T5 (cooled from hot-working and artificially aged) is suitable for extrusions that require immediate strength. The T651 designation indicates a T6 schedule with a controlled stretching (strain relief) operation to reduce residual stresses; this is important for machined or precision components. Overaging or improper aging cycles can reduce peak strength and alter toughness, so heat treatment cycles must be tailored to section thickness and desired aging response.

High-Temperature Performance

EN AW-6061 maintains usable mechanical properties up to roughly 120–150 °C, but notable strength loss occurs with prolonged exposure above this band due to coarsening of strengthening precipitates. For continuous service at elevated temperatures, designers should assume reduced yield and tensile strengths and consider creep behavior that becomes significant above ~150–200 °C. Oxidation is minimal compared with ferrous alloys, but thermal exposure can change surface finish and dimensional stability.

Welded assemblies and heat-affected zones are particularly sensitive to elevated temperatures because the precipitate distribution that provides strength can be altered locally, leading to soft zones. For high-temperature structural applications, 6061 should be limited to intermittent thermal exposure or combined with protective coatings and thermal design measures to avoid premature weakening. When designs must operate at elevated temperatures long-term, select alloys engineered for high-temperature stability or incorporate heavier safety factors.

Applications

Industry	Example Component	Why EN AW-6061 Is Used
Automotive	Suspension components, brackets	Good strength-to-weight, machinability and weldability
Marine	Structural frames, railings	Decent corrosion resistance and ease of fabrication
Aerospace	Fittings, substructures, interior components	Balance of strength, weight savings and predictable heat treatment response
Electronics	Heat sinks, enclosures	High thermal conductivity and formability for extrusions
General Manufacturing	Extruded profiles, machined parts	Broad availability in multiple tempers and product forms

EN AW-6061 finds use across sectors where a combination of moderate-to-high strength, corrosion resistance, and ease of fabrication are required. Its adaptability to extrusion, sheet, plate and bar production modes makes it a go-to alloy for parts where post-processing such as machining or welding is required. The consistent availability of T6 and T651 tempers permits designers to specify materials with predictable performance for production parts.

Selection Insights

Choose EN AW-6061 when you need a middle ground between high-strength heat-treatable alloys and highly formable commercial-purity aluminum. It trades off some electrical and thermal conductivity and ultimate formability compared with commercially pure 1100, but offers substantially higher tensile and yield strength while retaining reasonable corrosion resistance and machinability. Against work-hardened alloys like 3003 or 5052, 6061 delivers higher strength at the expense of some formability and may require heat treatment management for optimum results.

Compared with 6063, which is optimized for extrusion surface finish and extrudability, 6061 is preferred when greater structural strength and machinability are required despite slightly lower extrudability and surface finish. When corrosion resistance in aggressive marine environments is paramount, consider 5xxx series alloys, but select 6061 where machinability, availability of T6 temper and a predictable aging response are primary drivers. In procurement, specify the exact temper, thickness and applicable standard to ensure the material meets the design intent with known fabrication constraints.

Closing Summary

EN AW-6061 remains a cornerstone alloy in modern engineering due to its versatile combination of heat-treatable strength, good corrosion resistance, and broad manufacturability across sheet, plate, extrusion and bar forms. Its predictable response to standard heat treatment cycles, reasonable weldability and strong machinability make it suitable for a wide array of structural and thermal-management applications. For many designers and manufacturers the alloy represents the pragmatic choice where balanced performance, cost and supply-chain reliability are required.