Aluminum 6201: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

6201 is a member of the 6xxx series aluminum alloys (Al‑Mg‑Si family) that are heat‑treatable and designed for a combination of moderate strength, good extrudability, and reasonable corrosion resistance. The primary alloying elements are magnesium and silicon which form Mg2Si precipitates on aging; minor additions and controlled impurities (Fe, Mn, Cu, Cr, Ti) are used to tune mechanical and processing behavior.

Strengthening in 6201 is achieved principally by solution heat treatment followed by quenching and artificial aging (precipitation hardening), although some property tuning is possible by controlled cold work prior to aging. Key traits include moderate-to-high strength in heat treated tempers, good anodizability, good formability in soft tempers, and acceptable weldability with attention to HAZ softening; this combination makes 6201 useful where a balance of extrusion performance, structural strength and conductivity is required.

Typical industries using 6201 include transportation (structural extrusions and functional components), electrical and power transmission (conductor and busbar applications where conductivity and strength must be balanced), architectural extrusions, and some mechanical components requiring extruded profiles. Engineers choose 6201 over other alloys when they need a compromise between the high strength of 6xxx alloys like 6061 and the better extrudability and conductivity of alloys tailored for conductor use, or when a specific profile geometry benefits from 6201’s flow and aging characteristics.

Compared with other 6xxx alloys, 6201 is often selected for specific product forms (extrusions, drawn conductors) and thermal processing windows; it gives good precipitation hardening response while maintaining acceptable corrosion resistance and surface finish for anodizing or painting.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition, maximum ductility for forming
T4	Medium	Medium-High	Good	Good	Solution heat treated and naturally aged; good balance of formability and strength
T6	High	Low-Medium	Fair	Fair	Solution treated and artificially aged to peak strength; common for structural applications
T5	Medium-High	Medium	Good	Good	Cooled from hot working and artificially aged; often used for extrusions with immediate aging
T651	High	Low	Fair	Fair	Solution treated, stress relieved by stretching, then artificially aged; reduced residual stress for machining
H14	Medium	Low-Medium	Limited	Good	Strain‑hardened and partially annealed to a stable cold‑worked temper; used for formed sheet parts

Tempering strongly changes 6201’s mechanical performance because Mg2Si precipitation state controls yield and tensile strength. Soft tempers (O, T4) are used where forming and drawing are primary operations, whereas T5/T6/T651 are chosen when dimensional stability and peak strength are required for service; weldability and HAZ softening must be considered for welded assemblies.

Chemical Composition

Element	% Range	Notes
Si	0.5–1.2	Promotes Mg2Si precipitation; controls strength and extrusion fluidity
Fe	0.0–0.7	Impurity; increases strength and reduces ductility and surface finish if high
Mn	0.0–0.5	Grain refinement and improved toughness; often low in conductor grades
Mg	0.4–0.9	Primary strengthening element through Mg2Si formation
Cu	0.0–0.2	Small additions can boost strength but reduce corrosion resistance
Zn	0.0–0.2	Typically low; higher Zn can increase strength but reduce SCC resistance
Cr	0.0–0.25	Controls grain structure and recrystallization during processing
Ti	0.0–0.15	Used as grain refiner in cast or wrought products
Others (each)	0.0–0.05	Trace elements and residuals; balance aluminum

The composition is tuned to optimize precipitation hardening (Mg + Si) while keeping impurities low to preserve conductivity and surface finish. Small additions of elements such as Cr and Mn help control recrystallization and grain growth during hot working and subsequent thermal cycles, which supports better dimensional control and fatigue performance.

Mechanical Properties

Tensile behavior in 6201 is characteristic of heat‑treatable Al‑Mg‑Si alloys: soft and highly ductile in annealed or T4 conditions with a wide plastic range, and higher strength with reduced elongation in T5/T6 tempers due to a fine dispersion of Mg2Si precipitates. Yield and ultimate strength scale strongly with aging schedule, prior cold work and section thickness; thin extrusions reach peak properties faster and more uniformly than thick sections.

Hardness follows precipitation state and typically increases from ~35 HB in O condition to ~70–95 HB in peak aged T6, with corresponding increases in yield and tensile. Fatigue resistance is influenced by surface finish, extrusion defects and local porosity; properly processed and age‑treated 6201 exhibits good high‑cycle fatigue for structural extrusions but is less fatigue resistant than some 2xxx/7xxx high‑strength alloys.

Thickness and section geometry affect solution and aging kinetics; thicker sections cool more slowly and may require modified aging schedules to avoid underage in core regions. Manufacturing steps such as stretch straightening (for T651) and controlled pre‑aging cold work can tailor the yield/elongation trade off for specific forming or service requirements.

Property	O/Annealed	Key Temper (e.g., T6)	Notes
Tensile Strength	~90–140 MPa	~240–310 MPa	UTS depends on aging and section thickness; typical peak aged range shown
Yield Strength	~40–80 MPa	~130–260 MPa	YS increases markedly with precipitation; cold work prior to aging raises yield
Elongation	~20–35%	~6–14%	Ductility reduced in peak aged conditions; elongation depends on section and testing direction
Hardness	~25–40 HB	~70–95 HB	Brinell numbers approximate; hardness correlates with precipitate distribution

Physical Properties

Property	Value	Notes
Density	2.68–2.70 g/cm³	Typical for Al‑Mg‑Si alloys; useful for strength-to-weight calculations
Melting Range	~580–650 °C (solidus–liquidus window)	Alloying slightly lowers and broadens melting interval versus pure Al
Thermal Conductivity	140–170 W/m·K	Lower than pure Al but sufficient for many thermal management uses
Electrical Conductivity	~30–45 % IACS	Lower than pure Al; conductivity traded for strength via alloying
Specific Heat	~0.90 kJ/kg·K (900 J/kg·K)	Typical value for aluminum alloys at ambient temperatures
Thermal Expansion	~23–24 µm/m·K (23–24 ×10⁻⁶ /K)	Typical thermal expansion for Al alloys, important for joint design

6201 retains aluminum’s favorable combination of low density and good thermal properties, which is why it is often used in conductive or heat‑dissipating structures where mass savings matter. Thermal and electrical conductivities are reduced relative to pure aluminum due to solute scattering from Mg and Si; design should account for these reductions when conductivity is critical.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Thin gauge responds quickly to aging; good formability in O/T4	O, H14, T4	Used for formed panels and light structural components
Plate	6–50+ mm	Thick sections have slower heat transfer; may show lower core properties after aging	O, T4, T651	Thick plates require tailored heat treatments to ensure uniform properties
Extrusion	Wall sections from 1–100+ mm	Excellent extrudability; peak aged for strength	T5, T6, T651	Common for complex profiles, rails, busbars and structural members
Tube	Φ few mm to large diameters	Properties vary with cold drawing and aging	O, T4, T6	Used for structural tubing and conductor sleeves
Bar/Rod	Ø few mm to 50+ mm	Solid sections influenced by cooling rates	O, T6	Used for machined components and studs

Forming and processing differ significantly between sheets and extrusions: extrusions benefit from 6201’s flow during hot work and respond well to immediate aging (T5) or post‑extrusion solutionizing and aging (T6). Plates and thick sections require longer solution times or modified aging to develop consistent properties through the section, while thin gauges are more forgiving and are commonly used in formed components or drawn products.

Equivalent Grades

Standard	Grade	Region	Notes
AA	6201	USA	Designation under Aluminum Association for wrought 6201 alloy
EN AW	6201	Europe	Commonly cited as EN AW‑6201; chemistry and tempers aligned with AA standards
JIS	—	Japan	No direct one‑to‑one JIS grade; similar behavior to JIS A6061/A6063 family depending on temper
GB/T	—	China	Not always listed as a distinct GB grade; comparable to domestic Al‑Mg‑Si wrought alloys

Equivalent naming and specification practice varies by region; EN AW‑6201 and AA 6201 are typically compatible in composition and tempers, but details such as impurity limits, mechanical property testing directions, and accepted tempers may differ. Where direct equivalence is absent in national standards (JIS, GB/T), engineers substitute the closest Al‑Mg‑Si alloys with matching composition and temper response and verify by mechanical and electrical testing for critical applications.

Corrosion Resistance

6201 exhibits good general atmospheric corrosion resistance similar to other Al‑Mg‑Si alloys because the aluminum oxide layer passivates the surface and minor alloying elements do not strongly compromise pitting resistance. In rural and urban atmospheres the alloy performs well, and it takes decorative finishes or anodizing readily, which further enhances corrosion protection and wear resistance.

In marine or chloride‑rich environments 6201 is moderately resistant but less tolerant than Al‑Mg (5xxx) alloys specifically designed for seawater exposure; crevice and pitting corrosion can initiate at scratches, welds or in locations with trapped salt. For prolonged marine exposure, protective coatings, anodizing, or selection of higher corrosion‑resistant alloys is recommended, and attention to galvanic couples is required.

Stress corrosion cracking (SCC) susceptibility for 6xxx alloys is low relative to high‑strength 2xxx and 7xxx series alloys, but overaged or underaged microstructures and tensile residual stresses near welds can increase risk. Galvanic interactions with more noble metals (copper, stainless steel) can accelerate localized corrosion of 6201, so electrical insulation or sacrificial anodes should be considered in multiphase assemblies.

Fabrication Properties

Weldability

6201 is generally weldable by common fusion processes (TIG/GTAW, MIG/GMAW) and can be joined with appropriate filler alloys (commonly 4043 (Al‑Si) or 5356 (Al‑Mg) depending on required strength and corrosion resistance). Welds experience HAZ softening due to dissolution and coarsening of precipitates; designers should allow for reduced strength in weld zones and consider post‑weld heat treatment or mechanical design to avoid load concentrations at welded joints.

Machinability

Machinability of 6201 is moderate and similar to other 6xxx series alloys; cutting is typically smooth with continuous chips in soft tempers and shorter, more fragmented chips in peak aged tempers. Carbide tooling with positive rake and adequate coolant are recommended for turning and milling; feed and speed should be optimized to avoid built‑up edge, and stress relieving may be needed to minimize distortion in machined parts.

Formability

Forming performance is excellent in O and T4 tempers, enabling bending, deep drawing and complex profile forming with relatively low springback. Bend radii should follow general aluminum rules (minimum internal radius ~1–2× thickness for most operations) and springback compensation must account for the temper and aging state. Forming after solution treatment typically requires aging or stabilization to control dimensional changes in service.

Heat Treatment Behavior

6201 responds to standard heat treatment sequences for Al‑Mg‑Si alloys: solution treatment in the range of ~520–560 °C to dissolve Mg2Si into solid solution, rapid quenching to retain a supersaturated matrix, followed by natural aging (T4) or controlled artificial aging (T5/T6) to precipitate fine Mg2Si and develop strength. Aging schedules vary (e.g., 160–180 °C for several hours) depending on section size and desired property balance between strength and ductility.

T temper transitions are controlled by time‑temperature schedules: underaging gives higher ductility and lower yield, peak aging (T6) maximizes strength, and overaging reduces strength while improving toughness and SCC resistance. T651 (solution treated, stretch‑straightened, artificially aged) is commonly used where residual stress reduction and dimensional stability are required.

For non‑heat‑treatable manufacturing steps, work hardening can raise yield modestly but is not the primary strengthening mechanism for 6201; full annealing (O) restores maximum ductility and is used prior to forming or drawing operations.

High-Temperature Performance

Service strength of 6201 begins to decline at moderately elevated temperatures as precipitates coarsen and the supersaturated matrix relaxes; long‑term stability above ~120–150 °C will reduce peak aged strength significantly and is not recommended for structural applications. Short exposures up to ~100–120 °C typically have limited impact on properties if the material is not held at temperature long enough to promote overaging.

Oxidation at high temperature is limited by the protective alumina scale, but prolonged high‑temperature exposure in aggressive atmospheres can change surface chemistry and reduce fatigue life. The HAZ adjacent to welds is particularly vulnerable to softening at elevated temperatures, and design must account for potential creep or relaxation if parts operate in warm service conditions.

Applications

Industry	Example Component	Why 6201 Is Used
Automotive	Extruded structural profiles, trim rails	Good balance of extrudability, strength and finishability for complex profiles
Marine	Non‑critical structural sections, fittings	Adequate corrosion resistance and ability to be anodized for protective finish
Aerospace	Secondary internal fittings, conductive busbars	Favorable strength‑to‑weight and good fatigue and machinability when processed correctly
Electrical	Busbars, conductors, connector profiles	Reasonable electrical conductivity combined with improved mechanical strength relative to pure Al
Architecture	Window frames, curtain wall extrusions	Excellent surface finish, anodizing capability, and dimensional control after aging

6201 is most often selected for extruded profiles that require a combination of structural performance, good surface finish and the ability to be fabricated into complex shapes. Its adaptability to different tempers and post‑processing (anodizing, painting) makes it a common choice where both aesthetics and function are important.

Selection Insights

Choose 6201 when you require a heat‑treatable Al‑Mg‑Si alloy that balances extrusion performance, moderate to high strength and acceptable conductivity for conductor or busbar uses. It is a good mid‑range alloy for engineered extrusions where T5/T6 tempers provide the necessary strength without the higher cost and processing complexity of very high strength alloys.

Compared with commercially pure aluminum (1100), 6201 trades higher mechanical strength and better dimensional stability for reduced electrical and thermal conductivity; use 6201 where strength is a priority but some conductivity must be retained. Compared with work‑hardened alloys like 3003 or 5052, 6201 sits higher in strength (when aged) but offers slightly less innate corrosion resistance in severe chloride environments; choose 6201 for structural extrusions rather than for constant seawater exposure. Compared with common heat‑treatable alloys such as 6061/6063, 6201 is selected when extrudability and conductor‑style processing windows are preferred, or when a specific balance of precipitation kinetics and surface finish is required despite comparable or slightly lower peak strength.

Closing Summary

6201 remains a relevant aluminum alloy for modern engineering because it delivers a practical compromise of extrusion performance, heat‑treatable strength, and surface finishability, making it valuable for structural profiles, conductive components and architectural applications where balanced mechanical, thermal and corrosion properties are required.