Aluminum 6005: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

6005 is a member of the 6xxx series aluminum alloys, which are Al-Mg-Si alloys primarily strengthened by precipitate hardening. It sits in the family of heat-treatable aluminum alloys and is often specified for structural extrusions and wrought products where a balance of strength, extrusion performance, and corrosion resistance is required.

The principal alloying elements in 6005 are silicon and magnesium, which combine to form Mg2Si precipitates during aging and provide the primary strengthening mechanism. Trace additions of iron, manganese, chromium and copper influence grain structure, strength, and response to heat treatment while limiting detrimental intermetallics.

6005 exhibits a combination of moderate-to-high strength, good corrosion resistance in many atmospheres, reasonable weldability, and acceptable formability in softer tempers. These traits make it common in automotive structural members, architectural extrusions, railway components, and medium-duty structural applications where higher-strength 6xxx alloys like 6061 are not necessary or where extrusion characteristics are prioritized.

Engineers select 6005 when a compromise between 6063-like extrudability and 6061-like strength is needed, or where the alloy’s alloying balance produces favorable surface finish and aging response for long extrusions. Its cost, availability in extrusion billets and profiles, and predictable temper responses make it a practical choice for medium-duty structural components.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, maximum ductility for forming
H14	Low-Medium	Moderate	Good	Good	Strain-hardened to a specified temper, limited strengthening
T5	Medium	Moderate	Good	Good	Cooled from elevated temperature shaping and artificially aged
T6	Medium-High	Moderate-Low	Fair	Good	Solution heat treated and artificially aged to reach near-peak strength
T651	Medium-High	Moderate-Low	Fair	Good	Solution heat treated, stress-relieved by stretching, and artificially aged
T6511	Medium-High	Moderate-Low	Fair	Good	Similar to T651 with controlled stretching to reduce residual stresses

Temper selection strongly affects mechanical performance and formability. Annealed (O) tempers maximize ductility for deep drawing and forming operations, whereas T6/T651 variants maximize static strength at the cost of reduced elongation and more limited forming.

For welded structures, T5 and T6 offer good base-metal strength but the heat-affected zone (HAZ) will soften relative to the parent metal; designers must account for localized reductions and select tempers consistent with forming and post-fabrication treatment plans.

Chemical Composition

Element	% Range	Notes
Si	0.6–1.0	Provides solid-solution strength and forms Mg2Si precipitates with Mg
Fe	0.35 max	Impurity element; forms intermetallics that can reduce ductility and surface finish
Mn	0.05–0.20	Refines grain structure and controls recrystallization
Mg	0.4–0.8	Combines with Si to form Mg2Si precipitates; primary strengthening element
Cu	0.1–0.3	Small additions increase strength but may reduce corrosion resistance slightly
Zn	0.05 max	Typically low; higher amounts not intentional
Cr	0.05–0.25	Added to control grain growth and improve toughness during thermal processing
Ti	0.1 max	Grain refiner for cast/ingot processing; used in small amounts
Others	Balance Al, minor impurities	Total of other elements controlled to tight limits per specification

The Mg and Si balance determines the quantity and distribution of Mg2Si precipitates after heat treatment, which controls yield and tensile strengths. Iron and other impurities form coarse intermetallics that can impair ductility and surface appearance, so melt and casting practices are critical to maintain performance.

Small additions of Cr, Mn, and Ti are instrumental in controlling grain size and recrystallization during extrusion and thermal processing, improving mechanical homogeneity and reducing the tendency for hot shortness during hot working.

Mechanical Properties

In tensile behavior, 6005 in the T6/T651 range typically exhibits higher yield and ultimate tensile strength compared with 6xxx alloys optimized for extrudability, while retaining moderate elongation. Yield strength generally increases substantially from the O to T6 temper due to the precipitation of fine Mg2Si particles; however, elongation correspondingly decreases, and ductility must be evaluated relative to section thickness and forming history.

Hardness correlates with temper: annealed material has low hardness values suitable for forming, while artificially aged tempers reach significantly higher hardness and static strength. Fatigue performance in 6xxx alloys like 6005 is governed by surface finish, residual stress state, and section thickness; thicker sections and poor surface quality reduce fatigue life due to larger inherent defects and slower crack arrest.

Thickness affects mechanical response because cooling rates during quenching, and subsequent aging behavior, vary with section size; thicker extrusions may show lower peak strength after the same heat treatment and can have wider HAZ soft zones after welding. Designers should account for anisotropy introduced by extrusion and for property gradients through wall thickness when specifying safety factors.

Property	O/Annealed	Key Temper (e.g., T6/T651)	Notes
Tensile Strength	~160–220 MPa	~250–310 MPa	Values depend on tempers, section thickness and specific temper control
Yield Strength	~60–120 MPa	~210–260 MPa	Substantial gain due to precipitation hardening in T6/T651
Elongation	~18–30%	~6–12%	Higher elongation in O; T6 shows reduced ductility suitable for limited forming
Hardness	Low (HV 40–60)	Medium-High (HV 70–100)	Hardness tracks tensile strength and aging condition

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for wrought aluminum alloys; useful for mass calculations
Melting Range	~555–650 °C	Alloyed aluminum shows a melting/solidus range; process limits for welding and heat treatment
Thermal Conductivity	~150–165 W/(m·K)	Lower than pure Al but still high, useful for heat-dissipating structures
Electrical Conductivity	~32–38% IACS	Lower than pure Al due to alloying; suitable for some conductive applications with trade-offs
Specific Heat	~0.9 J/(g·K)	Typical aluminum specific heat for thermal mass calculations
Thermal Expansion	~23–24 µm/(m·K)	Moderate coefficient; relevant for thermal cycling and interference fits

6005 retains the intrinsic advantages of aluminum: low density and high specific strength compared to ferrous metals, combined with good thermal conductivity for many heat-transfer components. The presence of alloying elements reduces thermal and electrical conductivity relative to pure Al, but this is often acceptable for structural applications.

Thermal expansion and conductivity should be quantified in design when mating to dissimilar materials or when designing heat-dissipating parts, since thermal mismatch can induce stresses or gaps in assemblies across operating temperature ranges.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.4–6 mm	Good uniformity; temper-dependent strength	O, H14, T5, T6	Used for light panels, cladding, and formed parts
Plate	>6 mm up to 100 mm	Strength reduction possible in very thick sections	T6, T651	Thicker plates require controlled quench to achieve uniform properties
Extrusion	Complex profiles, wall thickness 1–30 mm	Excellent when properly homogenized; anisotropy along extrusion direction	T5, T6, T651	Common form for structural profiles, rails, and frames
Tube	Diameter-variable	Similar to extrusions; wall thickness influences aging	O, T5, T6	Structural tubing and rail applications
Bar/Rod	Ø3–120 mm	Bars retain as-extruded properties; machining often performed from T6/T651	O, T6	Used for machined fittings and structural pins

Processing route strongly affects final properties: extrusions are typically homogenized and solution-treated to mitigate segregation before aging, whereas sheet and plate production relies on rolling schedules to control grain structure. Extruded profiles may present mechanical anisotropy and directional properties that must be considered in structural design.

Forming, machining, and joining each impose different constraints: thin sheets favor forming in softer tempers while extruded profiles are commonly aged to T5/T6 for final dimensional stability and strength. Choice of product form should reflect downstream fabrication steps and required end-use performance.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6005	USA	American Aluminum Association designation for wrought alloy
EN AW	6005A / 6005	Europe	EN variants such as 6005A exist; chemistry and tempers are aligned but specification details may differ
JIS	—	Japan	No single direct JIS equivalent; closest families are Al-Mg-Si series (e.g., A6063/A6061) with different chemistries
GB/T	—	China	Chinese standards often have similar Al-Mg-Si grades but direct one-to-one equivalents can vary in Si/Mg balance

There is not always a perfect one-to-one equivalence between regional standards; the EN AW-6005A designation is the closest European counterpart but small chemistry and processing tolerances can produce different aging responses. When substituting grades across standards, verify key chemical limits, temper designations, and mechanical test data rather than relying solely on grade name.

Suppliers and specifications sometimes prefer 6005A for improved extrudability; purchasers should confirm whether 6005 or 6005A is intended, and reconcile temper and mechanical property requirements between standards during procurement.

Corrosion Resistance

In atmospheric environments, 6005 exhibits good general corrosion resistance characteristic of 6xxx alloys, with a naturally forming alumina film that protects the substrate. It performs well for outdoor architectural and structural applications provided air-born contaminants and aggressive environments are managed.

In marine or chloride-rich environments, 6005 is susceptible to localized corrosion such as pitting and crevice corrosion if protective coatings or anodizing are not used. Its resistance to stress corrosion cracking is moderate; susceptibility increases with tensile stress levels, aggressive electrolytes, and the presence of tensile residual stresses or weld-induced soft zones.

Galvanic interactions must be considered when coupling 6005 to more noble materials such as stainless steel or copper; without insulating barriers, accelerated corrosion of the aluminum is likely. Compared with 5xxx magnesium-containing alloys, 6005 trades some intrinsic corrosion resistance for higher strength and better heat-treatable properties, and it often benefits more from surface treatments like anodizing for long-term durability.

Fabrication Properties

Weldability

6005 is generally weldable by common fusion and solid-state methods such as MIG (GMAW), TIG (GTAW), and friction stir welding (FSW). The HAZ will typically soften from the peak-aged temper, so designers must account for local reductions in strength and potential need for post-weld heat treatment or design compensation.

Recommended filler alloys include 4043 (Al-Si) and 5356 (Al-Mg) depending on joint requirements and desired properties; 4043 reduces hot-cracking risk while 5356 can provide higher strength but requires care with corrosion behavior. Friction stir welding is often preferred for structural extrusions to minimize HAZ softening and produce superior mechanical properties relative to fusion welding.

Machinability

6005 exhibits fair machinability compared with free-machining aluminum alloys; its alloying level increases strength and reduces machinability index relative to 2xxx or 7xxx series. Carbide tooling with positive rake angles, rigid fixturing, and high spindle speeds produce the best surface finish and tool life.

Recommended strategies include shallow depth-of-cut finishing passes, high feed rates for chip breakup, and effective chip evacuation. Machining hardened or T6 tempers will increase cutting forces and tool wear; if heavy machining is required, sourcing softer tempers or performing solution/anneal steps prior to machining can improve tool life.

Formability

Formability is excellent in the O condition and good in H14/H16 strain-hardened tempers for moderate forming operations. For severe bending, drawing, or stretch-forming, start in an annealed or lightly worked temper before performing any artificial aging to regain strength.

Cold-work increases dislocation density and can be used to produce H-series tempers for parts requiring moderate strength without aging. Bending radii should follow typical aluminum forming guidelines: maintain minimum inside bend radius of approximately 1–2× material thickness in softer tempers and increase radius in stronger, aged tempers to avoid cracking.

Heat Treatment Behavior

As a heat-treatable alloy, 6005 responds to solution treatment, quenching, and artificial aging to develop precipitate-strengthened conditions. Typical solution treatment temperatures are in the range of approximately 520–560 °C to dissolve Mg2Si and homogenize the microstructure, followed by rapid quenching to retain a supersaturated solid solution.

Artificial aging (precipitation heat treatment) is performed at temperatures around 160–200 °C to control precipitate size and distribution; these treatments produce T5 or T6 type tempers. T5 refers to cooling from elevated-temperature processing then artificial aging, while T6 indicates solution heat treatment plus artificial aging for near-peak properties.

Overaging (T7 styles) reduces strength but improves resistance to stress corrosion cracking and imparts more dimensional stability for high-temperature exposure; selection between T5, T6 and T7 balances strength, toughness and environmental performance. Control of quench rate and aging schedule is particularly important for thicker sections to avoid property gradients.

High-Temperature Performance

6005 maintains useful properties at moderately elevated temperatures but experiences progressive strength loss as temperature increases above typical service ranges. Practical design limits for static strength are often below 120–150 °C; sustained exposure above these temperatures accelerates overaging and softens the alloy due to coarsening of Mg2Si precipitates.

Creep resistance of 6005 is limited compared with high-temperature alloys; designers should avoid sustained loading at elevated temperatures where dimensional stability is critical. Oxidation is minimal for aluminum in atmospheric oxygen at typical operating temperatures; however, at high service temperatures the protective oxide may scale differently, and corrosion mechanisms can change in aggressive environments.

Welded regions and the HAZ are particularly sensitive to thermal exposure; post-weld heat treatment or design allowances for reduced local strength are advisable if welded assemblies will operate at elevated temperatures.

Applications

Industry	Example Component	Why 6005 Is Used
Automotive	Structural extrusions, rails	Good strength-to-weight, extrusion capability for complex profiles
Marine	Superstructure components, railings	Balanced corrosion resistance and mechanical strength for exposed environments
Aerospace	Secondary structural fittings, slide rails	Favorable strength-to-weight and machinability for non-critical structural parts
Electronics	Heat-dissipating frames and chassis	Reasonable thermal conductivity combined with structural integrity

6005 is commonly selected for medium-duty structural profiles where extrudability, surface finish, and adequate strength are required. Its combination of producibility and mechanical properties makes it especially suitable for long extruded members, architectural framing, and components requiring stable properties after aging.

Selection Insights

Choose 6005 when you need an extrudable Al-Mg-Si alloy with better mechanical strength than pure aluminum and some 3xxx/5xxx work-hardened alloys, but with better extrusion and surface-finish characteristics than higher-strength 6xxx variants. It is well-suited to structural extrusions, medium-thickness plates and applications where post-form aging or controlled tempers are practical.

Compared with commercially pure aluminum (1100), 6005 trades higher strength and lower electrical/thermal conductivity for structural capability. Compared with work-hardened alloys such as 3003 or 5052, 6005 provides substantially higher strength at the expense of some ductility and slightly lower corrosion performance in very aggressive chloride environments. Compared with common heat-treatable alloys like 6061 or 6063, 6005 sits between them: it can offer better extrusion characteristics and specific property balances, and is sometimes selected when 6061’s peak strength is not required but better extrusion performance than 6063 is desired.

In short, pick 6005 when extrusion geometry, surface quality, and a moderate-to-high strength target are primary drivers, and when the fabrication plan can manage tempering, welding, and potential HAZ softening.

Closing Summary

6005 remains relevant for modern engineering because it delivers a practical combination of extrudability, predictable heat-treatment response, and moderate-to-high strength for structural applications. Its balanced chemistry and fabrication versatility make it a reliable choice for medium-duty structural components where cost, manufacturability, and consistent performance are essential.