Aluminum 6005A: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

6005A is a member of the 6xxx series aluminum alloys, a family defined by the Mg-Si binary system. This series is known for being heat-treatable by precipitation hardening (aging) and frequently used where a balance of strength, formability and corrosion resistance is required.

The primary alloying elements in 6005A are silicon and magnesium, which combine to form Mg2Si precipitates during aging and provide the principal strengthening mechanism. Secondary elements (Fe, Cu, Mn, Cr, Ti and trace additions) are controlled to optimize extrusion characteristics and to limit detrimental intermetallics that can impair toughness or weldability.

6005A displays medium to high strength for a wrought Al-Mg-Si alloy with good atmospheric corrosion resistance, reasonable weldability, and moderate formability depending on temper. It is commonly used in structural extrusions, architectural profiles, transportation components and other applications that require a favorable strength-to-weight ratio combined with good surface finish and dimensional stability.

Engineers choose 6005A over other alloys when extrusion productivity, dimensional accuracy, and post-aging stability are priorities. The alloy is often preferred to higher-strength 6xxx variants because it offers improved extrudability and more consistent mechanical properties in heavier sections, while offering better strength than the more formable 6063 in certain tempers.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–30%)	Excellent	Excellent	Fully annealed; maximum ductility and formability
H14	Low-Medium	Moderate (12–20%)	Good	Excellent	Strain-hardened, limited drawing; not heat-treated
T5	Medium	Moderate (10–16%)	Good	Good	Cooled from hot working and artificially aged; common for extrusions
T6	High	Low-Moderate (8–14%)	Fair	Good	Solution treated, quenched and artificially aged; peak strength
T651 / T6511	High	Low-Moderate (8–14%)	Fair	Good	T6 with stress-relief (stretcher- or stabilized) for improved dimensional stability
T6511	High	Low-Moderate (8–14%)	Fair	Good	Similar to T651; common for extruded profiles requiring straightness

Temper directly controls the microstructure through either work hardening or precipitation hardening, which in turn modifies yield/tensile strengths and ductility. Selection of T5, T6 or T651 variants is often driven by whether dimensional stability (T651) or maximum formability (O/H-temper) is the overriding requirement.

Chemical Composition

Element	% Range	Notes
Si	0.6 – 1.0	Provides solute for Mg2Si precipitates; aids castability and extrusion flow.
Fe	≤ 0.35	Impurity element; forms intermetallics that reduce ductility and impact extrudability.
Mn	≤ 0.15	Small additions can modify intermetallic morphology and improve strength slightly.
Mg	0.45 – 0.90	Primary strengthening element in combination with Si (Mg2Si formation).
Cu	≤ 0.20	Minor; increases strength but can reduce corrosion resistance if present at higher levels.
Zn	≤ 0.10	Kept low to avoid embrittlement and galvanic issues.
Cr	≤ 0.10	Controls grain structure and can inhibit recrystallization in stress-relief tempers.
Ti	≤ 0.10	Grain refiner when intentionally added; otherwise kept low.
Others (each)	≤ 0.05	Limits on other elements to maintain consistent aging behavior; Al balance

The Si/Mg ratio is the critical compositional control for precipitation hardening behavior in 6005A. Tight control of Fe and Mn helps ensure acceptable toughness and extrusion surface quality, while small additions of Cr or Ti are used to stabilize grain structure and to improve the response to solution treatment and aging.

Mechanical Properties

Tensile behavior in 6005A is controlled by precipitate size and distribution (Mg2Si) created during artificial aging. In annealed (O) condition the alloy is ductile with low yield and tensile strengths suitable for heavy forming. In T5/T6 tempers, fine, uniformly distributed precipitates raise both yield and ultimate tensile strengths while reducing total elongation.

Yield and fatigue performance are sensitive to section thickness and heat treatment uniformity; thicker sections can under-age in the centre, reducing effective strength and fatigue life. Hardness correlates with yield strength in these alloys and typically increases significantly after solution heat treatment and peak artificial aging; however, overaging can improve ductility at the expense of some strength.

Property	O/Annealed	Key Temper (T5 / T6 / T651)	Notes
Tensile Strength	120 – 160 MPa	240 – 315 MPa	Values depend on section thickness and exact temper; T6 provides peak strength.
Yield Strength	55 – 95 MPa	170 – 275 MPa	T6 and T651 variants show higher and more stable yield for structural use.
Elongation	18 – 30%	8 – 14%	Ductility drops as strength increases with aging and work hardening.
Hardness (HB)	35 – 55 HB	70 – 95 HB	Hardness increases with precipitation; hardness is a quick field proxy for temper verification.

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for wrought aluminum alloys; favorable strength-to-weight ratio.
Melting Range	555 – 650 °C (approx.)	Solidus–liquidus ranges vary with alloying; melting behaviour influences heat treatment limits.
Thermal Conductivity	~150 – 170 W/(m·K)	Lower than pure Al due to alloying; still good for heat-dissipation applications.
Electrical Conductivity	~28 – 40 % IACS	Reduced from pure Al; conductivity depends on temper and impurity levels.
Specific Heat	~900 J/(kg·K)	Typical of aluminum alloys near room temperature.
Thermal Expansion	~23.5 ×10^-6 /K	High coefficient relative to steels; important for thermal design and joint tolerances.

The physical property set places 6005A among alloys that balance mechanical performance with reasonable thermal and electrical conductivity. The alloy’s conductivity and thermal transport are good for many structural-thermal applications but are reduced from commercially pure aluminum by the Mg and Si solutes and precipitates.

Thermal expansion and conductivity must be factored into multi-material design, particularly at elevated temperatures or where differential expansion could create stresses in assemblies. The melting and solution-treatment temperature windows inform allowable thermal cycles during processing and fabrication.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5 – 6 mm	Thickness-sensitive; easier to solution-treat in thin gauges	O, T4, T5, T6	Widely used for clad and architectural panels.
Plate	> 6 mm up to ~100 mm	Centerline under-aging possible in thick plates	O, T6 (limited)	Plate requires careful heat treatment to avoid soft cores.
Extrusion	Variable cross-sections, long lengths	Excellent uniform mechanical properties when properly aged	T5, T6, T651	Primary commercial form for 6005A; optimized for complex profiles.
Tube	diameters from small to large, wall thickness variable	Performance depends on wall thickness and post-heat treatment	T5, T6	Structural and architectural tubing where straightness and surface finish matter.
Bar/Rod	Diameters up to ~200 mm	Machined parts often supplied in pre-aged condition	O, T6	Bars for fittings and machined components; larger diameters may show property gradients.

Extrusions are the dominant product form for 6005A because the alloy’s chemistry and processing window are tuned for good flow in extrusion dies and consistent aging response. Sheet and plate use is more limited by the need for uniform heat treatment, particularly in thicker sections where quench and aging across the cross-section become challenging.

Processing (e.g., quench rate, aging temperature and time) varies by product form to deliver target properties. Designers should specify both temper and any post-fabrication stabilization (T651) when dimensional stability is critical.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6005A	USA	Aluminum Association / ASTM designation commonly used in North America.
EN AW	6005A	Europe	EN designation often written as EN AW-6005A; composition and tolerances per EN standards.
JIS	Closest equivalents: A6061 / A6063 (comparative)	Japan	No exact one-to-one mapping; JIS alloys with similar Mg-Si content provide similar properties.
GB/T	6005 / 6005A (varies)	China	Chinese standards may list either 6005 or 6005A; manufacturing tolerances can differ modestly.

Subtle differences between standards commonly lie in impurity limits, allowed mechanical-property ranges for given tempers, and permitted heat-treatment/testing practices. When sourcing internationally, verify the specific standard version and the certificate of analysis because temper definitions and dimensional tolerances can cause performance variations in structural applications.

Corrosion Resistance

6005A offers good general atmospheric corrosion resistance typical of Mg-Si aluminum alloys, forming a stable oxide film that protects against uniform corrosion in mild environments. With appropriate surface preparation and coatings, the alloy performs well in architectural and many outdoor structural applications.

In marine or chloride-containing environments 6005A is reasonably resistant but not as robust as certain 5xxx (Al-Mg) series alloys for bare unpainted seawater service. Localized pitting can occur if protective coatings are breached, and selection of surface finish and protective systems is important for prolonged marine exposure.

Stress corrosion cracking susceptibility in 6xxx alloys is generally moderate and increases with higher strength tempers and tensile residual stresses; proper temper selection (avoid maximally aged states in highly stressed components) and post-weld repairs are standard mitigation measures. When coupled galvanically with more noble metals (e.g., copper, stainless steels), aluminum will act anodically; designers should include insulating barriers or select compatible materials to control galvanic currents.

Compared to 2xxx or 7xxx series alloys, 6005A is superior in corrosion resistance while offering lower maximum strength. Relative to 5xxx alloys it trades some corrosion robustness for higher achievable strength after aging, making 6005A a common compromise alloy for outdoor structural and architectural applications.

Fabrication Properties

Weldability

6005A welds well with common fusion processes (TIG/MIG) when appropriate filler metals and practices are used. Typical filler alloys are 4043 (Al-Si) for improved fluidity and lower cracking tendency or 5356 (Al-Mg) where higher strength in the weld is required; filler selection depends on desired weld mechanical properties and corrosion performance. Expect HAZ softening after fusion welding due to dissolution and re-precipitation of Mg2Si; post-weld artificial aging or localized heat treatment is often required to restore strength in structural weldments.

Machinability

Machinability of 6005A is moderate; it is less free-cutting than some 2xxx and 7xxx alloys but generally easier to machine than many high-strength alloys due to its ductile matrix. Carbide tooling with positive rake geometries and rigid set-ups yield best surface finishes and tool life; moderate cutting speeds and higher feed per tooth reduce built-up edge. Chip control is normally acceptable, producing short to moderately curled chips depending on temper and section size.

Formability

Formability is highest in O and H-temper conditions and decreases markedly after precipitation hardening. Bending radii of 2–3× material thickness are common starting guidelines for T-tempered sheet, while O temper can accommodate tighter radii and deeper draws. For complex forming operations, perform forming in O or T4 conditions and follow with controlled solution treatment and artificial aging to achieve final strength and dimensional stability.

Heat Treatment Behavior

As a heat-treatable alloy, 6005A responds to solution treatment, quenching and artificial aging by precipitation of Mg2Si. Typical solution-treatment temperatures are in the range of 520–540 °C with soak times adjusted for section thickness to ensure dissolution of coarse precipitates. Rapid quenching is required to retain a supersaturated solid solution prior to artificial aging.

Artificial aging temperatures commonly fall between 150–200 °C (T5/T6 regimes), with lower temperatures producing longer aging times and a finer precipitate distribution for improved toughness. Overaging at higher temperature or longer duration coarsens precipitates, reducing strength but improving ductility and stress-corrosion resistance; this trade-off is used deliberately in some applications to balance performance attributes.

Non-heat-treatable strengthening in Al alloys comes from work hardening, but for 6005A design intent typically uses solution/age routes to exploit higher strength capability. When using T651 (stress-relieved) tempers, a stabilization/stretch step after quenching is used to minimize residual stress and dimensional instability while preserving elevated strength.

High-Temperature Performance

6005A experiences notable strength loss as service temperature increases above roughly 120–150 °C due to coarsening and dissolution of strengthening precipitates. Continuous service at elevated temperatures accelerates overaging and reduces yield strength, thus design margins must account for temperature-dependent material properties.

Oxidation is limited for aluminum alloys at common engineering temperatures, but prolonged high-temperature exposure can alter surface appearance and degrade protective coatings. Heat-affected zones from welding or localized heating may overage and soften, potentially becoming the limiting factor in load-bearing joints if not re-aged or mechanically accounted for.

Applications

Industry	Example Component	Why 6005A Is Used
Automotive	Structural extruded rails, door impact beams	Good combination of extrusion quality, strength and surface finish
Marine	Architectural and structural profiles, non-critical structural members	Reasonable corrosion resistance with superior strength to common architectural alloys
Aerospace	Secondary structural fittings, fairings, stiffeners	Favorable strength-to-weight and dimensional stability for extruded profiles
Electronics	Heat sinks, chassis	Good thermal conductivity and machinability for fabricated components

6005A is frequently specified where complex extruded geometries must concurrently provide strength, aesthetics and predictable temper response after heat treatment. Its balance of properties makes it ideal for structural profiles that require both mechanical performance and good surface finish.

Selection Insights

6005A is selected where extrusion geometry and dimensional stability after aging are priorities, and where designers require higher strength than 6063 but better extrudability than some higher-strength 6xxx variants. Choose 6005A for long structural profiles that will be post-aged to T5/T6/T651 conditions.

Compared with commercially pure aluminum (1100), 6005A sacrifices electrical conductivity and formability for substantially higher strength and improved stiffness. Compared with work-hardened alloys like 3003 or 5052, 6005A offers higher achievable strength after aging and similar or slightly reduced corrosion resistance, making it preferable where structural capacity is critical.

Compared to common heat-treatable alloys such as 6061 or 6063, 6005A is often chosen when extrudability and section stability are more important than absolute peak strength; 6061 can provide higher peak strength in some conditions, but 6005A can produce more dimensionally accurate extrusions and better surface quality for certain profiles.

Closing Summary

6005A remains a practical engineering alloy for structural extrusions and profiles due to its controlled Mg-Si chemistry, reliable precipitation-hardening response and balanced combination of strength, corrosion resistance and manufacturability. Its predictable behavior across tempers and forms keeps it relevant for architectural, transportation and industrial applications where extrudability and post-heat-treatment stability are essential.