Aluminum 6067: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

AA 6067 is a member of the 6xxx series of aluminum alloys, which are Al-Mg-Si heat-treatable alloys commonly used for structural and extrusion applications. The alloy is primarily alloyed with magnesium and silicon to form Mg2Si precipitates for strengthening, with controlled additions of copper, chromium, titanium and trace elements to tailor strength and thermal stability.

The strengthening mechanism for 6067 is predominantly precipitation hardening combined with the potential for post-form cold work; it is a heat-treatable alloy offering T5/T6/T651 tempers for elevated strength and O/H tempers for enhanced formability. Key traits include a high strength-to-weight ratio relative to common 1xxx/3xxx series alloys, good corrosion resistance typical of the 6xxx family, favourable weldability with appropriate filler choices, and moderate formability that degrades in peak-aged conditions.

Industries that deploy 6067 commonly include aerospace and defense for structural extrusions and fittings, railway and heavy transport for high-strength extruded profiles, and specialized civil and industrial sectors where a balance of high strength, machinability and corrosion resistance are required. Engineers select 6067 when they need higher as-quenched and aged strength than 6061 or 6063 while still retaining reasonably good extrudability and thermal stability for thicker sections.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–35%)	Excellent	Excellent	Fully annealed; best for forming and bending
H14	Medium	Moderate (10–20%)	Good	Excellent	Strain-hardened to intermediate strength
T5	Medium-High	Moderate (8–15%)	Fair	Good	Cooled from elevated temperature and artificially aged
T6	High	Moderate-Low (8–12%)	Limited	Good	Solution heat-treated and artificially aged for peak strength
T651	High	Moderate-Low (8–12%)	Limited	Good	Solution heat-treated, stress-relieved by stretching, then artificially aged
T6511	High	Moderate-Low (8–12%)	Limited	Good	Similar to T651 with different straightening procedures
H111 / H112	Medium	Variable (10–20%)	Good	Excellent	Commercial tempers for extruded profiles with partial annealing

Temper has a significant effect on the balance between strength and manufacturability for 6067; O and H1x tempers give the best ductility and are preferred for severe forming operations. Peak-aged tempers (T6/T651) maximize tensile and yield strengths but reduce bendability and increase sensitivity to HAZ softening during welding.

Chemical Composition

Element	% Range	Notes
Si	0.4–0.8	Forms Mg2Si precipitates; controls strength and extrusion behavior
Fe	0.3–0.7	Impurity element; excessive Fe reduces ductility and promotes intermetallics
Mn	0.05–0.20	Low additions to control grain structure and improve toughness
Mg	0.6–1.1	Primary strengthening element in combination with Si
Cu	0.15–0.4	Small addition to raise strength and improve aging response
Zn	0.0–0.25	Usually low; higher amounts can alter aging and corrosion behavior
Cr	0.05–0.25	Controls grain structure and reduces susceptibility to recrystallization
Ti	0.04–0.15	Grain refiner for castings/extrusions and to stabilize microstructure
Others (each)	≤0.05	Residual elements (Ni, Pb, Sn) controlled; total others ≤0.15–0.20

The Al-Mg-Si system in 6067 is tuned so that Mg and Si combine to form a controllable population of Mg2Si precipitates during aging; small Cu and Cr additions modify precipitate chemistry and distribution to increase yield strength and improve elevated-temperature stability. Trace elements and maximum allowable impurities are kept low to preserve toughness, formability and weldability.

Mechanical Properties

Tensile behavior of 6067 is characteristic of heat-treatable 6xxx alloys: a well-defined yield plateau in peak-aged tempers followed by progressive strain hardening. In the annealed condition the alloy exhibits high elongation and low yield, transitioning to much higher yield and ultimate strengths after solutionizing, quenching and artificial aging.

Hardness correlates closely with temper and precipitation state; peak-aged conditions (T6/T651) produce hardness values in the high range for 6xxx alloys while O/H conditions are markedly softer and more ductile. Fatigue behavior is reasonable for cyclic loads; fatigue strength is typically a fraction of ultimate tensile strength and is sensitive to surface finish, residual stresses and welds.

Thickness influences achievable strength in T6-type tempers because solute and precipitate distributions and quench rates vary with section size; thicker sections may show reduced peak strength and wider property scatter compared with thin extrusions or sheet.

Property	O/Annealed	Key Temper (T6/T651)	Notes
Tensile Strength	100–160 MPa	320–360 MPa	Values are typical ranges; depends on section thickness and aging schedule
Yield Strength	35–80 MPa	280–320 MPa	T6/T651 yields are much higher due to precipitate strengthening
Elongation	20–35%	8–12%	Elongation drops with increasing temper and strength
Hardness (Brinell)	30–60 HB	85–105 HB	Hardness increases with age; thicker sections can show lower hardness after quench

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for 6xxx aluminum alloys
Melting Range	~582–652 °C	Solidus–liquidus range dependent on composition and impurity levels
Thermal Conductivity	140–170 W/m·K	Lower than pure Al; decreases slightly with alloying and aging
Electrical Conductivity	~34–42 % IACS	Dependent on temper and alloying; conductivity drops with increased Cu/Mg
Specific Heat	~0.90 J/g·K	Near that of other Al-Mg-Si alloys at ambient temperatures
Thermal Expansion	~23–24 ×10⁻⁶ /K	Typical linear coefficient for Al alloys at room temperature

These physical constants guide design decisions for heat transfer and thermal stress analysis; the alloy retains excellent thermal conductivity compared to steels, but not as high as pure aluminum. Electrical conductivity is moderate and usually adequate for many structural/electronic components but is reduced by alloying elements compared with pure Al.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Uniform, good surface quality	O, H14, T4, T6	Used for formed panels and fabricated parts
Plate	6–100 mm	Reduced peak attainable strength in thick plates	O, T6 (limited)	Thick sections sensitive to quench; often supplied in T351/T651 variants
Extrusion	Wall thickness 1–50 mm	Optimized for directional strength	T4, T5, T6, T651	Widely used for high-strength structural profiles
Tube	Ø 10–300 mm	Section-specific properties	O, T6	Seamless or welded; used for structural tubing and pressure applications
Bar/Rod	Ø 5–100 mm	Good machinability	O, T6	Used for machined fittings, fasteners and extruded dowels

Sheets and thin extrusions achieve peak-aged properties more readily due to efficient quenching, while plates and thick sections often require modified aging or T651-like sequences to control distortion and residual stresses. Extrusion processing benefits from 6067’s balanced flow characteristics, and the alloy is often chosen when stronger extruded profiles are needed compared with 6061 or 6063.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6067	USA	Primary Aluminum Association / ASTM designation
EN AW	6067	Europe	EN designation commonly mirrors AA numbers for wrought alloys
JIS	A6067	Japan	Japanese standard often uses A-prefix with similar composition control
GB/T	6067	China	Chinese national standard generally aligns with AA composition ranges

Equivalent grade listings are often the same numeric designation across major standards for wrought aluminum alloys, but processing controls, permitted impurity limits and mechanical property requirements can vary by specification. Buyers should verify the procurement specification (e.g., ASTM, EN, JIS, GB/T) for exact tensile/yield and acceptance criteria rather than relying solely on alloy number.

Corrosion Resistance

Atmospheric corrosion resistance of 6067 is good for a heat-treatable 6xxx alloy; the naturally formed aluminum oxide film provides baseline protection and the alloy resists general corrosion in urban and industrial atmospheres. Localized corrosion (pitting) can occur in chloride-rich environments; proper surface treatments, anodizing or coatings are commonly specified for marine or coastal exposures.

In marine behavior 6067 is moderate: it performs better than 2xxx and many higher-strength Cu-rich alloys but is generally less resistant than 5xxx Mg-rich alloys in active chloride immersion scenarios. Welding and mechanical damage can expose bare aluminum and increase susceptibility to local attack, so post-weld corrosion protection and design to avoid crevices are recommended.

Stress corrosion cracking risk for 6xxx alloys is lower than for highly stressed, high-Cu alloys but is not negligible under high tensile residual or applied stresses in warm chloride environments. Galvanic interactions favor aluminum as the anodic partner when mated to steels, copper or stainless steel, so isolation, coatings or sacrificial anodes are typical design mitigations.

Fabrication Properties

6067 is engineered for a balance of extrudability, machinability and heat-treatable strength, and these fabrication characteristics must be managed by selecting appropriate tempers and post-processing sequences. Heat input during welding, quench severity after solution treatment and forming methods determine final properties and dimensional stability.

Weldability

6067 welds well with common arc processes (TIG/GTAW, MIG/GMAW) when using fillers matched to the base alloy system. Typical filler choices are 4043 (Al-Si) for improved flow and reduced hot cracking tendency or 5356 for higher strength in certain cases; 4043 is often preferred for T6 base metal to minimize underbead cracking. The heat-affected zone experiences softening due to precipitate dissolution and overaging, reducing local strength and necessitating post-weld mechanical or thermal treatments if full strength must be restored.

Machinability

Machinability of 6067 is moderate to good compared with other 6xxx alloys; it machines better than many work-hardened 5xxx alloys but not as well as free-cutting alloys like 2xxx with leaded additives. Carbide tooling with TiN or AlTiN coatings and rigid setups give best results; higher spindle speeds with moderate feed rates and chip breakers help control continuous chip formation. Surface finish and dimensional tolerance capability are high when machining pre-tempered or properly aged material.

Formability

Formability is best in O, H111 and H112 tempers where ductility is highest; cold forming in T6 or T5 conditions is limited and may require intermediate anneals or solution treatment plus re-ageing. Typical minimum inside bend radii depend on temper and thickness but a starting guideline is 1–3× thickness for O/H tempers and 3–6× thickness for T6-like tempers. Springback is significant in higher-strength tempers and must be accounted for in tooling and die design.

Heat Treatment Behavior

Solution treatment for 6067 typically targets the dissolution of Mg2Si and other strengthening phases at temperatures in the range of ~520–540 °C for wrought product, followed by rapid quenching to retain a supersaturated solid solution. Quench severity directly affects achievable peak strength; slow cooling or thick sections reduce the supersaturation and lower final strength.

Artificial aging schedules to reach T5/T6 conditions are generally in the 150–185 °C range for times varying from 4–24 hours depending on desired strength/stability trade-offs; overaging at higher temperatures or longer times increases toughness and stress-corrosion resistance at the expense of peak strength. The T651 designation indicates a solution-treated, stress-relieved by stretching, and artificially aged condition that improves dimensional stability for machined or structural parts.

For non-heat-treatable tempers, strengthening is achieved by controlled cold work (H tempers) and recovery/anneal treatments; full anneal (O) is typically performed near 415 °C for wrought sections to restore ductility and homogenize the microstructure.

High-Temperature Performance

6067 exhibits progressive loss of yield and tensile strength with increasing temperature; significant reductions in design strength typically occur above 100–150 °C, and prolonged exposure above ~200 °C will substantially reduce precipitate-strengthening effectiveness. Short-term elevated-temperature applications (intermittent up to ~150 °C) can be tolerated with some retention of mechanical properties, but creep resistance is limited compared with specialty elevated-temperature alloys.

The protective aluminum oxide layer confers good oxidation resistance at moderate temperatures, but mechanical scaling is not a primary concern for the typical service envelope of 6067. Heat-affected zones adjacent to welds can show degraded high-temperature performance due to precipitate coarsening and local property gradients.

Applications

Industry	Example Component	Why 6067 Is Used
Aerospace	Structural extrusions, fittings, longerons	High strength-to-weight, good extrusion characteristics, improved aging stability
Marine & Transport	Railcar structural members, heavy vehicle frames	Balanced corrosion resistance and higher strength for welded extrusions
Civil / Architectural	High-strength curtain wall extrusions, profiles	Dimensional stability (T651) and attractive surface finish for anodizing
Electronics / Thermal	Heat-transfer brackets, housings	Adequate thermal conductivity with high stiffness and machinability
Industrial Machinery	High-strength fabricated frames and machined fittings	Good machinability and the ability to reach elevated yield strengths after aging

6067 is chosen in applications where extruded shapes or machined fittings require a higher as-aged strength level than common 6061/6063 can provide, combined with the corrosion resistance and fabrication properties of the 6xxx family.

Selection Insights

Select 6067 when a design requires higher aged yield strength from an extrudable, heat-treatable alloy but you still need reasonable weldability and corrosion resistance. Compared with 1100 (commercially pure aluminum), 6067 trades superior electrical and thermal conductivity plus excellent formability for substantially higher strength and stiffness; choose 1100 only where conductivity and ease of forming are paramount.

Against common work-hardened alloys such as 3003 or 5052, 6067 provides higher peak strength for structural uses while offering comparable atmospheric corrosion resistance; however, those Mg-rich work-hardening alloys will out-perform 6067 in severe marine immersion cases and in applications requiring large, cold-formed geometries. When compared to 6061 or 6063, 6067 is selected when improved aged strength or enhanced stability in thicker extrusions is required despite potentially higher alloy cost and somewhat reduced formability; 6061 remains attractive when broad availability and slightly lower cost are dominant factors.

Closing Summary

AA 6067 occupies a practical position within the 6xxx family as a higher-strength, heat-treatable alloy optimized for extrusions and machined structural components where a refined balance of strength, corrosion resistance and fabrication performance is needed. Its ability to reach elevated aged strengths with acceptable weldability and good machinability keeps it relevant for aerospace, transport and industrial applications that demand lightweight structural solutions.