Aluminum A2024: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A2024 is an aluminum-copper alloy belonging to the 2xxx series, characterized by aluminum matrix strengthened primarily by copper and magnesium additions. The alloy typically contains roughly 3.8–4.9% Cu, 1.2–1.8% Mg and smaller amounts of Mn, with the balance being Al and trace elements.

A2024 is a heat-treatable alloy that attains high static strength through solution heat treatment and precipitation hardening. Its principal traits are high tensile and fatigue strength, reasonable machinability, and moderate formability in softer tempers, while its corrosion resistance is inferior to many 5xxx and 6xxx series alloys and often requires surface protection for demanding environments.

Typical industries that specify A2024 include aerospace primary and secondary structures, high-strength forgings, truck and trailer components, and some marine components where strength-to-weight is critical and protective cladding is used. Engineers choose A2024 when a high specific strength and fatigue performance are primary design drivers, and when the parts can be protected or designed to mitigate corrosion and weldability limitations.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; best for forming and rework
H14	Medium-Low	Moderate	Good	Poor	Strain-hardened moderately; limited use vs T tempers
T3	High	Moderate	Fair	Poor	Solution heat-treated, cold worked, naturally aged
T4	Medium-High	Moderate	Fair	Poor	Solution treated and naturally aged; softer than T6
T6	High	Low-Moderate	Limited	Poor	Solution-treated then artificial aging; peak strength
T351 / T3511	High	Moderate	Fair	Poor	Solution-treated, stress-relieved by stretching; common for aircraft
T73	Medium	Moderate	Fair	Poor	Overaged to improve SCC resistance at some strength cost

Tempering changes the dominant deformation and failure modes because it alters precipitate size and distribution. Peak-aged tempers (T6/T3) maximize strength and fatigue resistance but reduce ductility and formability and worsen weldability due to HAZ softening.

Selecting a temper is a trade-off between manufacturability and in-service performance; designers commonly specify T351/T3 for aerospace structural parts where dimensional stability after quenching and stretch-relief are required.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.5	Common impurity; controlled to limit brittle intermetallics
Fe	≤ 0.5	Forms Fe-rich intermetallics that influence fracture and SCC
Mn	0.3–0.9	Improves strength via dispersoids and limits recrystallization
Mg	1.2–1.8	Contributes to precipitation (Mg-rich phases) and strength
Cu	3.8–4.9	Primary strengthening element; controls precipitation hardening
Zn	≤ 0.25	Minor; higher levels not desired for 2xxx balance
Cr	0.10–0.35	Grain structure control, limits grain growth during SA
Ti	≤ 0.15	Grain refiner during solidification and ingot processing
Others (each)	≤ 0.05	Trace elements controlled to meet mechanical and corrosion specs

Copper and magnesium are the active elements that form coherent and semi-coherent precipitates (S' and S phases) during aging and are responsible for the alloy's high strength. Manganese and chromium act as microstructure stabilizers, controlling grain size and dispersoid chemistry to improve toughness and resistance to recrystallization.

Mechanical Properties

A2024 shows high ultimate and yield strengths when in T3/T6 family tempers because of a fine distribution of Cu- and Mg-bearing precipitates. The alloy is favored in fatigue-critical applications due to its combination of high static strength and favorable crack-growth behavior, but susceptibility to localized corrosion can accelerate crack initiation if not protected.

Yield and tensile strength are thickness and temper dependent, with thin-sheet specimens generally reaching higher strengths for the same temper. Elongation is moderate in peak-aged tempers and substantially higher in annealed condition; hardness follows the same trend as tensile properties and can drop substantially in the HAZ of welded joints.

Fatigue properties are generally excellent for an aluminum alloy; crack initiation life benefits from good surface finish and corrosion protection, and the crack growth rates are lower than many non-heat-treatable aluminum alloys. Thickness effects are noticeable: thicker sections may have coarser precipitate distributions and lower hardening response after quench and age cycles.

Property	O/Annealed	Key Temper (T3 / T6 / T351)	Notes
Tensile Strength (UTS)	~240–300 MPa	~430–490 MPa	Values depend on temper and thickness; T6 near peak values
Yield Strength (0.2% offset)	~70–150 MPa	~300–365 MPa	T3/T6 yield is high; annealed yields are low
Elongation (A%)	~20–30%	~10–20%	T6 tends to have lower elongation than T3 or O
Hardness (HB)	~45–70 HB	~120–160 HB	Hardness correlates with precipitate state and mechanical properties

Physical Properties

Property	Value	Notes
Density	2.78 g/cm³	High strength-to-weight compared with steel alloys
Melting Range	~500–640 °C	Solidus and liquidus shifted by alloying vs pure Al
Thermal Conductivity	~120–150 W/m·K	Lower than pure Al but still good for heat spreading
Electrical Conductivity	~30–40 %IACS	Reduced from pure Al due to alloying elements
Specific Heat	~0.88–0.90 J/g·K	Typical aluminum specific heat near room temperature
Thermal Expansion	~23–24 µm/m·K	Similar coefficient to other Al alloys; design for thermal strain

The density and thermal properties make A2024 attractive where weight savings and moderate thermal management are required. Thermal conductivity and expansion should be considered in assemblies with dissimilar materials to avoid thermal stress and galvanic concerns.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6 mm	Uniform through-thickness in thin gauges	O, T3, T6, T351	Most common form for aircraft skins and structural panels
Plate	>6 mm up to ~150 mm	Can show through-thickness strength gradients	T3, T6, T73	Thick sections require controlled quench and aging to avoid soft cores
Extrusion	Limited cross-sections	Less common due to casting/extrusion cracking risk	T6 (ageable)	Extruded profiles exist but are less widespread than 6xxx alloys
Tube	OD 10–150 mm, wall dependent	Good fatigue strength when seamless	T3, T6	Used for high-strength tubular structures and trusses
Bar/Rod	Diameters varied	Good machinability in most tempers	O, T6	Forged and drawn bars for fittings and fasteners

Processing routes (cold rolling, forging, extrusion) influence final properties via texture and residual stress. Plate and heavy forgings require careful heat treatment and quench control to avoid soft zones and to obtain uniform mechanical performance through thickness.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A2024	USA	Primary designation for wrought products
EN AW	2024	Europe	EN AW-2024 commonly used; specifications may differ on impurity limits
JIS	A2017 / A2024 equiv	Japan	A2017/2024 family members have similar Cu-Mg content but different limits
GB/T	2A02 / 2024	China	2A02 is the Chinese series equivalence used in national standards

Equivalency tables are approximate because individual standards set different impurity and mechanical acceptance limits and may specify different testing protocols. Users should cross-check temper designations and certification specs when substituting material from different standards or regions.

Corrosion Resistance

A2024 has modest atmospheric resistance in open, dry environments but is vulnerable to localized corrosion and pitting in marine and chloride-containing atmospheres. Unclad 2024 alloys exposed to seawater or splash zones will corrode relatively rapidly compared to 5xxx and 6xxx series alloys, so designers commonly use Alclad cladding, anodizing, or organic coatings for protection.

Stress corrosion cracking is a known concern for 2xxx series alloys, especially in peak-aged tempers under tensile stresses and corrosive environments. Overaged tempers such as T73 or local design choices that reduce residual tensile stresses can mitigate SCC risk at the expense of some strength.

Galvanic interaction with dissimilar metals is an important design consideration; when coupled to cathodic metals like stainless steel, 2024 will act anodically and corrode preferentially. Compared with 6xxx and 5xxx alloys, A2024 provides higher strength but significantly lower bare-environment corrosion performance, which must be offset by protective strategies.

Fabrication Properties

Weldability

Welding A2024 is challenging due to hot cracking susceptibility and significant HAZ softening that reduces strength relative to base material. Gas tungsten arc welding (TIG) and gas metal arc welding (MIG) can be used with specialized filler alloys such as 2319, but welded joints rarely match the strength of T3/T6 base metal without subsequent localized heat treatment. For structural applications, mechanical fastening, bonding, or riveted assemblies are commonly preferred over welded joints.

Machinability

A2024 is generally regarded as having good machinability among high-strength aluminum alloys, with well-behaved chips and good surface finish when using sharp carbide tooling and abundant coolant. Machining indexes are typically in the 60–80% range relative to free-machining aluminum references, and feed-rich strategies with positive rake tools help control built-up edge. Tooling recommendations include carbide inserts, robust chip control, and interrupted cut considerations for forgings and cast-to-shape components.

Formability

Forming is best performed in softer tempers such as O or H1x and is limited in peak-aged conditions where ductility is reduced. Bend radii should be conservative; a minimum inside bend radius of around 2–3 times the material thickness is a practical starting point for T3/T6 sheets, while O-temper material can be bent to tighter radii. If forming is required for high-strength parts, adopt pre-forming anneal or choose tempering sequences (form in O, then solution treat and age) to achieve final mechanical properties.

Heat Treatment Behavior

A2024 is a heat-treatable alloy and responds strongly to solution treatment and controlled aging. Typical solution treatment temperatures are in the 495–500 °C range to dissolve copper and magnesium into solid solution, followed by rapid quenching to retain supersaturation. Natural aging (T4/T3 variants) yields partial strengthening over time while artificial aging (T6) at approximately 160–200 °C for several hours precipitates the strengthening phases to reach peak hardness.

Temper transitions like T3 (solution treatment, cold work, natural age) and T6 (solution treat, quench, artificial age) change precipitate morphology from fine coherent clusters to larger semi-coherent S' precipitates, driving significant strength increases. Overaging (T73) produces coarser precipitates that improve resistance to stress corrosion cracking while lowering peak strength, a trade-off used in aggressive-service components.

Non-heat-treatable tempering for A2024 is limited; cold working provides some strengthening, but full-strength restoration after cold work requires heat treatment sequences that are specific to 2xxx alloys and must be performed with quench control to avoid property gradients.

High-Temperature Performance

A2024 loses substantial strength as temperature increases above about 100–150 °C, and it is typically not specified for continuous service at elevated temperatures. Creep resistance is limited compared with higher-temperature alloys and steels, and prolonged exposure near aging temperatures can lead to overaging and softening of peak-aged tempers. Oxidation is minimal compared to steels, but the mechanical property degradation and possible precipitate coarsening limit long-term use above ambient conditions.

For welded structures, the HAZ is particularly susceptible to thermal cycles producing soft zones; these areas can control failure under cyclic loading at elevated temperatures. Design for thermal cycles and service temperature must include allowances for loss of yield and tensile strength as well as potential accelerated corrosion kinetics.

Applications

Industry	Example Component	Why A2024 Is Used
Aerospace	Wing skins, fuselage frames, fittings	High specific strength and fatigue performance
Marine	Structural members with cladding	Strength-to-weight for non-exposed structures
Automotive	Suspension and structural components	High static and fatigue strength where weight matters
Defense	Missile and ordnance components	Good strength and machinability for precision parts
Electronics	Structural heat spreaders and housings	Balance of stiffness, machinability, and thermal conductivity

A2024 remains a material of choice where high static and fatigue strength are required alongside good machinability and acceptable weight. Protective finishes and careful joint design are prerequisites for reliable long-term service in corrosive environments.

Selection Insights

Choose A2024 when the design priority is high tensile and fatigue strength combined with good machinability and when corrosion protection can be provided. Use T3/T351 for aerospace structural members where fatigue life and dimensional stability are critical, and consider T73 or cladding when SCC or marine exposure is a concern.

Compared with commercially pure aluminum (1100), A2024 trades electrical and thermal conductivity and superior formability for substantially higher strength and fatigue resistance, making it unsuitable where maximum conductivity or deep forming is required. Against work-hardened alloys like 3003 or 5052, A2024 delivers far higher strength but lower corrosion resistance and poorer weldability, so those alloys are preferred when corrosion resistance and joining ease dominate. Compared with common heat-treatable alloys such as 6061, A2024 typically offers higher fatigue strength and stiffness for the same mass, but with worse corrosion resistance and more difficult weldability; A2024 is selected when structural fatigue margins outweigh those trade-offs.

Closing Summary

A2024 remains a cornerstone high-strength aluminum alloy for aerospace and high-performance structural applications due to its excellent strength-to-weight and fatigue characteristics. Its use requires considered choices about temper, protective finishes, and joining methods to manage corrosion and weldability limitations, but when those factors are addressed it provides an efficient balance of mechanical performance and manufacturability.