Aluminum 2017A: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

2017A is a member of the 2xxx series aluminum-copper alloys, a class historically optimized for high strength through precipitation hardening. Its matrix is dominated by aluminum with copper as the principal alloying element, supplemented by manganese and small additions of magnesium, iron and trace elements that refine microstructure and control precipitate kinetics.

Strengthening in 2017A is primarily by heat-treatable precipitation hardening: solution treatment dissolves Cu-rich phases, quenching retains a supersaturated solid solution, and subsequent natural or artificial aging precipitates fine Al2Cu (θ') and related phases that raise yield and ultimate strength. This alloy exhibits a characteristic trade-off of elevated tensile strength versus reduced ductility and a susceptibility to localized corrosion and stress-corrosion cracking compared to non-heat-treatable alloys.

Key traits include high achievable static strength in T6-style tempers, reasonable fatigue performance when properly heat-treated and stress-relieved, and moderate thermal/electrical conductivity reduced relative to commercially pure aluminum. Typical industries using 2017A include aerospace and defense for fittings and forgings, transportation and automotive for structural connectors and rivets, and specialized hardware where strength-to-weight and machinability are prioritized.

Engineers select 2017A when a combination of high strength, good machinability and predictable aging response is required and the application can mitigate or tolerate its corrosion sensitivity and welding limitations. The alloy is preferred over some other high-strength series when fine control of precipitation and dimensional stability after aging are important for fitted assemblies.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed condition for maximum ductility
H14	Medium-High	Low-Moderate	Fair	Limited	Strain-hardened half-hard; increased strength via cold work
T4	Medium	Moderate	Good	Limited	Solution treated + natural aging; soft enough for forming prior to final aging
T6	High	Low	Fair	Poor	Solution treated + artificial aging; peak-strength condition used for structural parts
T651	High	Low	Fair	Poor	T6 with stress-relief by stretching or compressive treatment to minimize residual stress

Temper has a decisive effect on 2017A performance because precipitation state and dislocation structure control yield, ductility and fatigue. Annealed O material is used when deep forming is required, whereas T6/T651 are used where maximum static strength and dimensional stability are needed and forming is minimized.

Heat-treatment routes also influence susceptibility to stress-corrosion cracking and local galvanic behavior; stress-relieved tempers such as T651 or stretched tempers reduce distortion during machining and improve consistency in fatigue-critical applications.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.50	Deoxidizer and impurity; kept low to control intermetallics and machining behavior
Fe	≤ 0.70	Impurity forming intermetallic particles that affect machinability and corrosion initiation
Mn	0.30–1.00	Refines grain structure and improves strength and toughness
Mg	0.10–0.80	Minor contributor to strength via solid solution and promotes age-hardening interactions
Cu	3.5–4.5	Principal strengthening element; forms Al2Cu precipitates that determine peak strength
Zn	≤ 0.25	Low level; not a primary strengthening contributor in 2xxx alloys
Cr	≤ 0.10	Grain structure control and recrystallization inhibitor in some tempers
Ti	≤ 0.15	Grain refiner in castings and some wrought products
Others (each)	≤ 0.05	Trace elements controlled to maintain predictable aging and corrosion behavior

The relatively high copper content is the main driver of mechanical performance in 2017A by promoting a dense and fine distribution of θ' precipitates during aging. Manganese and chromium are present to control grain size, texture and recovery during heat treatment and mechanical processing, which helps balance strength, toughness and fatigue life.

Impurity levels of iron and silicon are kept low to limit coarse constituent phases that act as nucleation sites for corrosion and crack initiation; overall composition control is important for reproducible precipitation kinetics and mechanical properties across production lots.

Mechanical Properties

In tension 2017A exhibits a strong dependence on temper and thickness because precipitation hardening and cold work determine yield and ultimate strength. Peak-aged (T6/T651) conditions deliver the highest tensile and yield strengths but with a marked reduction in elongation and notch toughness compared with annealed material. Fatigue resistance is generally good for a heat-treated, stress-relieved part with well-controlled microstructure, but design must account for reduced corrosion fatigue resistance in chloride or humid environments.

Hardness tracks tensile behavior: annealed O conditions produce low Brinell values and high formability while T6/T651 produces significantly higher hardness that supports machining and wear resistance in service. Thickness effects are significant during solution treatment and aging; thick sections may compromise peak hardness and strength due to slower cooling rates and incomplete solutioning, so process parameters must be adjusted for large forgings or plates.

Property	O/Annealed	Key Temper (T6 / T651)	Notes
Tensile Strength	220–320 MPa	430–480 MPa	T6 values depend on section thickness and aging schedule
Yield Strength	100–160 MPa	350–420 MPa	Yield rises sharply with age-hardening and cold work
Elongation	18–30%	6–12%	Ductility reduced in peak-aged tempers; fracture modes can be more brittle
Hardness (HB)	50–80 HB	120–150 HB	Hardness correlated with precipitate density and dislocation interactions

Physical Properties

Property	Value	Notes
Density	2.78 g/cm³	Slightly higher than pure Al due to Cu content
Melting Range (approx.)	Solidus ~500°C – Liquidus ~640°C	Alloy melting interval; important for brazing and casting-related processes
Thermal Conductivity	~140–160 W/m·K (at 20°C)	Lower than pure Al; Cu reduces conductivity but remains adequate for many thermal applications
Electrical Conductivity	~30% IACS (typical)	Reduced by alloying; not intended for high-conductivity electrical leads
Specific Heat	~0.90 J/g·K (900 J/kg·K)	Typical of aluminum alloys at ambient temperatures
Thermal Expansion	~23.5 µm/m·K (20–100°C)	Similar to other Al alloys; relevant for fitted assemblies with dissimilar materials

The increased copper fraction reduces both thermal and electrical conductivity relative to commercially pure and 6xxx-series aluminum, but thermal performance remains acceptable for applications where conductivity is secondary to strength. The melting range indicates caution for thermal processing; brazing and localized heating should avoid temperatures approaching the solidus to prevent incipient melting and constituent liquation.

Thermal expansion is comparable to other aluminum alloys, so design of bolted or press-fit assemblies with mixed materials must account for differential thermal strains across expected service temperature ranges.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Good strength in T6; O for forming	O, H14, T4, T6	Widely used for panels, skins and fabricated parts
Plate	>6 mm up to 150+ mm	Thick sections may show reduced peak hardness	T6, T651	Larger parts require longer solution treatment and careful quenching
Extrusion	Profiles up to 200 mm cross-section	Strength depends on temper and subsequent aging	T4, T6	Extrusions enable complex cross-sections but require process control for properties
Tube	Ø10–300 mm	Similar to extrusions; wall thickness affects aging response	T6, T651	Common in structural and hydraulic applications when high strength is required
Bar/Rod	Ø4–150 mm	Bars offer high machinability in T6	T6, O	Used for fasteners, fittings and precision-machined components

Sheet and plate processing differ mainly in thermal mass and quenchability; plate requires longer soak times for full solutioning and more aggressive quenching strategies to avoid precipitate coarsening. Extrusions and tubes must be designed with consideration of temper transitions during heat treatment and the possibility of residual stresses that can be relieved via stretching or stabilization passes.

Formed or cold-worked products often go through a T4 → T6 sequence where parts are formed after solution treatment and natural aging, then artificially aged to final strength, balancing formability and final mechanical performance.

Equivalent Grades

Standard	Grade	Region	Notes
AA	2017A	USA/International	Common Aluminum Association designation for wrought Al-Cu-Mn alloy
EN AW	2017A	Europe	EN classification generally aligns compositionally but may have different control limits
JIS	A2017	Japan	Similar chemistry, with local tolerances and tempers tailored to JIS practices
GB/T	2A17 (or 2017A)	China	Chinese standard equivalents often listed as 2A17 with comparable composition ranges

Equivalent designations reflect broadly similar Al-Cu-Mn chemistries, but regional standards differ in specific impurity limits, permitted tempers and dimensional tolerances. Users should check certificate data for critical properties because small differences in Mn, Fe or Si can influence aging kinetics, toughness and corrosion resistance.

When substituting between standards, confirm mechanical property requirements and allowed tempers; some standards permit slightly different solution-treatment and aging schedules that affect final strength and residual stress levels.

Corrosion Resistance

In atmospheric environments 2017A shows moderate resistance but is more susceptible than 5xxx and 6xxx series alloys due to copper-rich intermetallics that act as cathodic sites. Localized corrosion such as pitting and intergranular attack may initiate at constituent particles or along grain boundaries, especially after improper heat treatment or in the presence of chloride ions. Protective coatings, anodizing and careful design to avoid crevices significantly mitigate these risks and are common practice for outdoor and marine-exposed parts.

Marine behavior is less favorable than marine-grade Al-Mg alloys; 2xxx alloys are typically avoided for primary hull structures in highly corrosive saltwater unless substantial corrosion protection and sacrificial anodes are employed. Stress corrosion cracking (SCC) is a known hazard for high-strength Al-Cu alloys under tensile stress in moist chloride environments and must be considered in the material selection and qualification process for critical components.

Galvanic interactions place 2017A at risk when coupled to more noble materials such as stainless steel; design should ensure insulating layers or sacrificial anodes to prevent galvanic acceleration of corrosion. Compared with 1xxx/3xxx/5xxx families, 2017A trades corrosion resistance for mechanical strength and requires additional surface protection in aggressive environments.

Fabrication Properties

Weldability

Welding 2017A by fusion processes (MIG/TIG) is challenging because Al-Cu alloys lose strength in the weld heat-affected zone and are prone to hot cracking and porosity. Solid-state joining methods such as friction stir welding (FSW) are often preferred for structural components because they lower the risk of liquation cracking and preserve more of the base-metal strength. When fusion welding is required, filler alloys designed for higher ductility and post-weld heat treatments are recommended, but designers must account for significant HAZ softening and potential re-precipitation effects.

Machinability

2017A exhibits good machinability relative to many aluminum alloys due to its higher strength and stable chip formation when in a T6 state; it machines with predictable tool wear and dimensional stability. Carbide tooling with appropriate coatings (TiN, AlTiN) and controlled speeds (moderate cutting speeds with robust feed) yield best results especially for interrupted cuts, while coolant control reduces built-up edge on tools. Chip morphology tends to be short segmented chips in harder tempers and continuous in annealed tempers; tooling geometry and coolant selection should be matched to temper and section thickness.

Formability

Formability is best in soft tempers such as O or T4 where ductility permits bending and drawing with modest radii; peak-aged T6 offers limited formability and is prone to cracking if cold-formed. Recommended minimum bend radii depend on temper and thickness but typically range from 2–6× material thickness for O and T4, and increase substantially for T6 where pre-forming before final aging is commonplace. Controlled warm forming and solution treat/form/age cycles are commonly used to achieve complex shapes while preserving final strength.

Heat Treatment Behavior

2017A is a heat-treatable alloy where solution treatment, quenching and aging define final mechanical properties. Typical solution treatment temperatures are in the range of 500–525°C, held to dissolve copper-rich phases into the aluminum matrix, followed by rapid quenching (water quench) to trap a supersaturated solid solution. Quench rate and section thickness are critical; slow cooling or inadequate quenching reduces precipitation driving force and lowers achievable peak strength.

Artificial aging is commonly performed at 150–190°C for periods of 4–12 hours depending on desired strength and toughness balance; the T6 designation corresponds to solutionized and artificially aged conditions tuned for peak strength. Natural aging (T4) can provide partial strengthening at ambient temperature but yields lower peak properties than controlled artificial aging and can be used as an intermediate step when parts must be formed prior to final aging.

Temper transitions such as T4 → T6 are frequently employed in fabrication workflows: parts are solution-treated and lightly aged to enable forming, then artificially aged to reach final mechanical properties. Stress-relief operations such as stretching (T651) reduce residual distortion and improve fatigue life for machined or fitted assemblies.

High-Temperature Performance

2017A retains useful strength at moderately elevated temperatures, but precipitate coarsening and over-aging begin to reduce strength significantly above roughly 150°C. Continuous service above 150–175°C will progressively degrade the fine precipitates responsible for hardening, leading to lowered yield and tensile values and increased ductility in the over-aged condition. Design for elevated-temperature applications should include accelerated aging tests and service-temperature qualification to quantify loss of mechanical integrity over time.

Oxidation is not a major concern for aluminum at moderate temperatures because of the protective alumina film, but localized overheating during welding or machining can cause surface liquation and loss of mechanical properties. The heat-affected zone near welds is particularly vulnerable to softening and precip