Aluminum A2017: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A2017 is an aluminum-copper alloy that sits in the 2xxx series of wrought aluminum alloys. The alloy's principal alloying element is copper, with secondary additions of manganese and small amounts of magnesium, chromium and silicon to tailor strength, grain structure and machinability.

A2017 is a heat-treatable (age-hardenable) alloy; its primary strengthening mechanism is precipitation hardening from solution treatment and artificial aging, augmented by controlled cold work in selected tempers. The combination of precipitation strengthening and fine-grain control produces substantially higher static and fatigue strength than typical pure or work-hardened alloys.

Key traits of A2017 include high strength-to-weight ratio, good machinability in certain tempers, moderate corrosion resistance (inferior to 5xxx and 6xxx families), and limited weldability compared with non-Cu alloys. Typical industries using A2017 are aerospace and defense for fittings and hardware, precision mechanical components in automotive and industrial equipment, and specialty forgings and extrusions where high strength and dimensional stability are required.

Engineers choose A2017 when a design requires higher strength and fatigue resistance than 1xxx/3xxx/5xxx series can provide while retaining good machinability for complex or precision parts. A2017 is selected over higher-corrosion-resistant alloys when mechanical performance, tight tolerance machining and local stiffness are priorities and when protective coatings or design details can mitigate corrosion exposure.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; best for forming and relieving residual stress
T4	Medium-High	Moderate	Good	Limited	Naturally aged after solution treatment; good balance of strength/formability
T6	High	Low-Moderate	Fair	Poor	Solution treated and artificially aged for maximum strength
T651	High	Low-Moderate	Fair	Poor	T6 with stress relief (stretch) to minimize residual stress and distortion
H1x / H2x (e.g., H14)	Variable	Reduced	Good-Fair	Limited	Combinations of cold work and aging; tailor strength and formability for specific parts

Temper has a major influence on A2017’s mechanical and fabrication behavior. Annealed O temper provides the best ductility and formability for deep drawing and complex bending, while solution-treated and artificially aged tempers (T6/T651) deliver peak strength and fatigue performance at the cost of reduced elongation.

Temper choice also affects machinability and distortion risk: harder tempers machine differently and are more susceptible to cracking during welding, whereas stress-relieved tempers (T651) reduce warping in tight-tolerance components.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.5	Controlled low silicon to limit brittle intermetallics and retain machinability
Fe	≤ 0.7	Residual impurity; excessive Fe forms hard intermetallics that impair toughness
Mn	0.3–0.9	Grain structure control and improved strength via dispersion of intermetallics
Mg	0.1–0.5	Minor contribution to precipitation; modifies aging response
Cu	3.5–5.5	Primary strengthening element; forms Al-Cu precipitates responsible for age hardening
Zn	≤ 0.25	Kept low to avoid unintended strengthening and corrosion sensitivity
Cr	0.05–0.25	Microstructure control; reduces recrystallization during thermomechanical processing
Ti	0.02–0.15	Grain refiner for cast or wrought products; improves toughness and structure
Others (each)	≤ 0.05	Trace elements and impurities; balance Al

The copper content is the defining factor for A2017’s mechanical performance: Cu-rich precipitates (θ′/θ phases) produced by solution treatment and aging provide the bulk of the alloy’s strength. Manganese and chromium refine grain size and limit the growth of undesirable intermetallics, preserving toughness and improving fatigue performance. Low silicon and zinc keep unwelcome brittle phases and galvanic risks under control, while titanium is used in small amounts as an inoculant for consistent microstructure during casting and working.

Mechanical Properties

A2017 exhibits pronounced differences between annealed and aged tempers. In annealed condition the alloy offers good ductility and moderate strength; in heat-treated and aged states it reaches substantially higher tensile and yield strengths due to fine Al–Cu precipitates. Elongation drops in the high-strength tempers and hardness rises accordingly, so the choice of temper must balance forming needs against final mechanical requirements.

Fatigue behavior is one of A2017’s strengths when properly heat treated and surface-finished, with good resistance to crack initiation compared with softer alloys; however, fatigue crack growth is sensitive to surface defects, corrosion and heat-affected zones from welding. Thickness and section size influence the obtainable properties: thicker sections are harder to quench effectively and may show lower peak hardness and strength after age hardening.

Quench sensitivity is an important processing concern—rapid cooling after solution treatment maximizes supersaturation and subsequent precipitation; inadequate quench rates produce lower strength and degraded fatigue behavior. The presence of copper also reduces tolerance for local heating (welding or machining-generated heat) because of HAZ softening.

Property	O/Annealed	Key Temper (T6/T651)	Notes
Tensile Strength	180–260 MPa	400–470 MPa	T6 achieves the alloy’s design strength via precipitation hardening
Yield Strength	75–140 MPa	340–400 MPa	Yield increases substantially after aging; values depend on exact temp/age cycle
Elongation	18–30%	8–12%	Ductility reduced in high-strength tempers; critical for forming operations
Hardness (HB)	60–85 HB	120–160 HB	Hardness follows tensile behavior; useful for quick QC checks

Physical Properties

Property	Value	Notes
Density	2.78 g/cm³	Slightly higher than pure Al due to copper content
Melting Range	~500–640 °C	Broad solidus–liquidus range typical of wrought Al–Cu alloys
Thermal Conductivity	~120–140 W/m·K	Lower than pure Al and non-Cu alloys due to copper and other solutes
Electrical Conductivity	~24–36 %IACS	Reduced by alloying; not suited for primary electrical conductors
Specific Heat	~880 J/kg·K	Comparable to other wrought aluminum alloys
Thermal Expansion	~23.5 µm/m·K	Typical aluminum thermal expansion; important for fit/tolerancing

A2017’s higher density and lower thermal/electrical conductivity relative to pure aluminum reflect the trade-off inherent in adding copper for strength. The alloy remains an efficient heat conductor for many applications, but designers should not expect the thermal or electrical performance of 1xxx-series alloys.

Thermal expansion and specific heat are close to other Al alloys, requiring designers to account for thermal growth in assemblies and fastened joints. The melting/solidus range informs heat-treatment windows and defines safe working temperatures for solution treatment and welding operations.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6 mm	Thin sheets achieve near-peak properties after heat treatment	O, T4, T6, T651	Used for precision panels and machined components after stabilization
Plate	6–100+ mm	Thick sections can be quench-sensitive; may have lower achieved strength	O, T4, T6 (with care)	Requires controlled quenching and sometimes overaging to stabilize
Extrusion	Variable cross-sections	Extrudability limited compared with 6xxx; mechanical properties depend on temper	T4, T6	Complex profiles possible but require careful control of cooling/aging
Tube	OD/ID per spec	Good for high-strength structural tubing when age hardened	O, T6	Welded or seamless options; HAZ considerations for welded tube
Bar/Rod	Diameters up to ~200 mm	Bars retain good machinability and take full heat-treatment response	O, T6	Common for turned components, fasteners, and aerospace fittings

Form affects processing strategy: thin-sheet components can be solution treated and quenched quickly to gain full strength, while thick plates and large extrusions require adjusted quench/age cycles to avoid property gradients. Extrusion and forging parameters differ from more commonly extruded 6xxx alloys; tooling and process windows must accommodate A2017’s higher strength and lower ductility in peak tempers.

Product choice also steers fabrication: sheet and bar typically go to machining and precision parts, while plate and extrusions suit structural components where larger sections are required. Welded tubular forms must manage HAZ softening through design and post-weld treatments.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A2017 / A2017A	USA	Common North American designation; A2017A often used to denote tighter control
EN AW	2017 / 2017A	Europe	EN AW-2017A typically cited for wrought products; check W.Nr. specifics
JIS	A2017	Japan	JIS nominally aligns with AA series for this alloy; local spec verification advised
GB/T	2017 / 2A17	China	Chinese standards generally list 2A17 as the comparable alloy; confirm processing classes

The alloy is broadly standardized, but small differences can exist between A2017 and A2017A (tightened composition/impurity limits) or between regional standards that govern allowable impurities and product forms. When substituting between specifications, review the exact chemistry and tempering schedules as mechanical properties and processing windows can change with slight compositional shifts.

Corrosion Resistance

A2017 has only moderate atmospheric corrosion resistance compared with 5xxx and 6xxx series alloys due to its copper content, which promotes localized active corrosion in some environments. In clean, mild atmospheres it performs acceptably, but exposure to industrial or marine atmospheres accelerates pitting and intergranular attack unless protected by coatings or cladding.

In marine and chloride-containing environments A2017 is more susceptible to localized corrosion and requires protective surface treatments (anodizing, conversion coatings, paint) and thoughtful design to avoid crevices and stray-current paths. The alloy can suffer stress-corrosion cracking (SCC) in the presence of tensile stresses and corrosive media; SCC sensitivity is increased in some tempers and when retained tensile residual stresses are present.

Galvanic interactions should be considered: A2017 is anodic to stainless steels and noble metals but cathodic to some magnesium alloys; coupling to dissimilar metals without isolation may accelerate local corrosion. Compared with 2xxx family peers, A2017’s corrosion behavior is typical for Al–Cu alloys; it is less corrosion-tolerant than Al–Mg alloys (5xxx) and many 6xxx alloys but generally more machinable and amenable to tight-tolerance components.

Fabrication Properties

Weldability

Welding of A2017 is challenging because copper-rich aluminum alloys are prone to hot cracking and HAZ softening. Fusion welding reduces local strength dramatically in the heat-affected zone and may require special filler metals (Aluminum–Si or Al–Cu fillers depending on application) and pre/post-weld procedures. For critical parts, brazing or mechanical fastening is commonly used instead of full-penetration welding, and if welding is unavoidable, design for larger welds with post-weld heat treatment where possible.

Machinability

A2017 is regarded as a good-to-excellent machinable alloy in many tempers; its higher hardness and strength produce short, controllable chips and good surface finish under appropriate tooling. Carbide tooling with positive rake and good coolant application is recommended; feeds and speeds are higher than for pure Al, and chip control features (peel-ins, chip breakers) can improve productivity. Tool wear is moderate; cutter geometry and coolant/lubrication control are important for tight-tolerance machining.

Formability

Cold forming capabilities are temper-dependent: O-temper offers excellent formability for bending and drawing, while T6 and similar peak-tempers have limited ductility and require larger bend radii. Typical minimum bend radii are several times material thickness in high-strength tempers, and stretch-forming with controlled pre-age or post-age sequences is often used for parts that require both accurate shape and high final strength.

Heat Treatment Behavior

A2017 is heat-treatable and reacts well to classical solution treatment and artificial aging cycles. Solution treatment is typically carried out near the alloy’s solidus—commonly in the 500–535 °C range—followed by a rapid quench to retain copper in supersaturated solid solution. Artificial aging is commonly performed at 160–190 °C to precipitate fine Al–Cu phases and achieve T6-type properties; aging time and temperature balance peak strength against overaging and stress-corrosion susceptibility.

Transition tempers such as T4 (natural aging) or controlled cold work plus aging (T651 variants) are used to achieve specific combinations of strength, distortion control and machinability. Overaging at higher temperatures or extended times reduces peak strength but can improve toughness and corrosion resistance; tailored thermal cycles are used to manage quench sensitivity in thick sections.

Non-heat-treatable behaviors apply only to the cold-worked tempers—work hardening (H1x/H2x) increases strength by dislocation accumulation but offers less sustained strengthening than precipitation routes. Full anneal (O) resets the microstructure and removes residual stresses for forming and machining operations.

High-Temperature Performance

A2017 experiences substantial strength loss at elevated temperatures; significant reductions occur above approximately 150–200 °C as precipitates coarsen and the matrix softens. Long-term exposure at elevated service temperatures accelerates overaging and reduces both static and fatigue strength, so continuous operation above these temperatures is generally avoided for load-bearing parts.

Oxidation is not a primary limiting mechanism for A2017 at moderate temperatures, but surface oxide formation can complicate protective coating adhesion and post-processing operations. The heat-affected zone of welded parts shows localized softening and reduced high-temperature capability, which must be accounted for in design by increasing section sizes or applying post-weld heat treatments when feasible.

Applications

Industry	Example Component	Why A2017 Is Used
Aerospace	Fittings, forgings, bushings	High strength-to-weight, good fatigue behavior after aging
Automotive	High-strength brackets, precision machined components	Machinability and strength for compact components
Marine	Structural fittings, non-primary hull hardware	Strength and dimensional stability with corrosion protection
Industrial Machinery	Gears housings, mounts	Good machinability and wear-resistant surfaces after heat treatment
Electronics	Chassis and connector bodies	Dimensional stability and machinability for precision assemblies

A2017’s combination of high strength, predictable aging response and good machinability make it a favored alloy for precision, high-stress components where dimensional control and fatigue life are critical. Protective finishes and design attention to corrosion-prone areas allow successful use in harsher environments.

Selection Insights

A2017 trades electrical and thermal conductivity and formability for higher strength compared with commercially pure aluminum (e.g., 1100). Choose A2017 when part strength, fatigue life and machinability are more important than maximum conductivity or the best possible forming behavior.

Compared with work-hardened alloys (3003 / 5052), A2017 provides substantially higher static and fatigue strength but has reduced corrosion resistance and weldability. Use A2017 for higher-loaded machined parts rather than general-sheet or forming applications where 3xxx/5xxx alloys shine.

Against common heat-treatable alloys (6061 / 6063), A2017 often offers higher age-hardened strength and superior machinability for certain hardware, but it is more sensitive to corrosion and welding. Prefer A2017 when peak strength, tight machining tolerances and fatigue resistance are critical and when corrosion control can be achieved through coatings or design.

Closing Summary

A2017 remains relevant for modern engineering where a strong, machinable aluminum alloy with reliable age-hardening response is required; its strengths are most effectively used in precision, high-load components when designers mitigate corrosion and welding limitations through protective finishes and considered design.