Aluminum 8007: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Alloy 8007 is part of the 8xxx series of aluminum alloys, a family often characterized by the inclusion of lithium as a principal alloying constituent alongside other microalloying additions. These alloys exploit lithium to reduce density and increase elastic modulus per unit mass, aiming to improve specific stiffness and weight-sensitive performance in structural applications.

8007 is formulated as a heat-treatable, precipitation‑strengthened aluminum alloy where the dominant strengthening mechanism is nucleation and growth of fine δ' (Al3Li) and other coherent precipitates during artificial aging. The microstructure can be tailored by solution treatment, quenching and controlled aging to generate a balance between strength, ductility and toughness suited to different tempers.

Key traits of 8007 include a favorable strength‑to‑weight ratio, lower density than conventional Al‑Mg‑Si and Al‑Cu alloys, and a stiffness increase relative to conventional alloys at comparable gauge. Corrosion resistance and weldability are strongly temper‑ and chemistry‑dependent, with formability generally best in annealed or partially annealed tempers and reduced in peak‑aged conditions.

Typical industries using 8007 include aerospace and space structures, high‑performance transportation (automotive and rail), specialized marine components, and select electronics/thermal management applications where reduced mass and increased stiffness are advantageous. Engineers select 8007 when the design premium is placed on specific stiffness and lightweighting combined with a requirement for moderate-to-high strength and acceptable corrosion and fatigue performance.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed, maximum ductility for forming
H111 / H14	Low-Medium	Medium-High	Very Good	Good	Light work‑hardening for modest strength gains
T3	Medium	Medium	Good	Fair	Solution treated, cold worked and naturally aged
T6	High	Low-Medium	Fair	Fair-Good	Solution treated and artificially aged for peak strength
T8 / T91	High	Low	Limited	Fair	Solution treated, cold worked and artificially aged (controlled)
T651	High	Low	Limited	Fair	Solution treated, stress‑relieved by stretching, artificially aged

Temper controls the balance between yield/UTS and ductility in 8007 by altering precipitate size, distribution and dislocation density. Annealed/O tempers maximize formability and are preferred for deep‑drawn parts, while T6 and similar tempers produce the highest tensile and yield strengths at the expense of elongation and bendability.

Aging path and amount of cold work greatly influence toughness, fatigue crack growth rates and susceptibility to localized corrosion; designers must choose a temper that aligns with forming operations and expected in‑service loading to avoid over‑treatment or insufficient strength.

Chemical Composition

Element	% Range	Notes
Si	0.10–0.50	Impurity control; forms intermetallics with Fe; limits fluidity in casting grades
Fe	0.05–0.60	Toughness and inclusion source; kept low to reduce coarse intermetallics
Mn	0.05–0.50	Grain structure control and strength via dispersoids
Mg	0.05–1.20	Contributes to age hardening and strength, interacts with Li/Al phases
Cu	0.05–2.00	Enhances strength via additional precipitates but can reduce corrosion resistance
Zn	0.00–2.00	Can assist strength but increases susceptibility to localized corrosion if high
Cr	0.01–0.30	Controls recrystallization and coarse grain growth during processing
Ti	0.01–0.20	Grain refiner in cast and wrought products, improves mechanical uniformity
Others (incl. Li)	Li 0.20–2.50 (typical)	Lithium is the defining element; other trace elements (Be, Zr) used for microstructure control

The chemistry of 8007 centers on lithium content as the defining performance driver, lowering density and enabling formation of δ' precipitates that provide high specific strength. Copper, magnesium and zinc are used to tune strength through additional precipitate phases but must be balanced to maintain corrosion resistance and fracture toughness. Controlled additions of Zr/Cr/Ti are common to refine grain structure, stabilize tensile properties during thermal cycles and reduce recrystallization.

Mechanical Properties

Tensile behavior in 8007 shows a wide spread depending on temper and product form; annealed (O) material typically exhibits modest ultimate tensile strength with high elongation, while T6/T8 tempers deliver significantly higher tensile and yield strengths at reduced ductility. The presence of fine, coherent Al3Li precipitates in peak‑aged conditions raises both yield and tensile strengths while retaining beneficial modulus increases.

Yield strength is sensitive to aging and cold work; T6 tempers commonly provide a substantial yield increase due to homogeneous precipitation, but localized overaging or coarse precipitates will reduce yield and toughness. Elongation drops in high‑strength tempers and is also reduced in thicker sections due to through‑thickness constraint and microstructural heterogeneity.

Fatigue performance of 8007 benefits from the alloy’s stiffness and precipitate dispersion when processed correctly; however, fatigue crack initiation and early propagation can be exacerbated by surface roughness, inclusions and galvanic couples. Thickness effects are notable: thin sections respond rapidly to solution and quench cycles producing more uniform properties, whereas thick sections can suffer from slower quench rates and reduced peak properties.

Property	O/Annealed	Key Temper (e.g., T6)	Notes
Tensile Strength	150–250 MPa (typ)	350–470 MPa (typ)	Ranges depend on Li content and heat treatment; T6 shows marked increase
Yield Strength	60–130 MPa (typ)	300–420 MPa (typ)	Yield increases with aging and cold work; HAZ can soften locally
Elongation	20–35%	7–15%	Ductility reduced with higher strength tempers and thicker gauges
Hardness	40–90 HB	90–140 HB	Hardness correlates with precipitate density and cold work

Physical Properties

Property	Value	Notes
Density	2.55–2.67 g/cm3	Lower than conventional aluminum due to Li; exact value varies with Li level
Melting Range	~ 520–650 °C	Alloying shifts solidus/liquidus; appropriate solution treatment temperatures must be observed
Thermal Conductivity	120–165 W/m·K	Lower than pure Al; conductivity depends on alloying elements and temper
Electrical Conductivity	25–48 %IACS	Reduced compared with pure Al; conductivity falls with solute content and work hardening
Specific Heat	~0.90 J/g·K	Similar order of magnitude to common Al alloys; varies modestly with alloying
Thermal Expansion	22–24 µm/m·K (20–100 °C)	Coefficient similar to many Al alloys but slightly influenced by Li content

The lowered density of 8007 is a primary physical advantage in weight‑sensitive designs and contributes to higher specific stiffness. Thermal and electrical conductivities are reduced over pure aluminum due to solute scattering; this must be considered for thermal management and electrical applications.

Thermal processing windows are critical: solution treatment and aging parameters must account for the alloy’s melting range and the stability of Li‑rich precipitates. Designers must also account for slightly different thermal expansion behavior when mating 8007 to dissimilar materials.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Good uniformity in thin gauges	O, H14, T3, T6	Common for aerospace skins and automotive panels
Plate	6–25 mm	Strength may reduce in thick sections due to quench sensitivity	O, T6 (limited)	Requires controlled processing to ensure through‑thickness properties
Extrusion	Cross‑sections up to 200 mm	Strength varies with section and age hardening	T6, T8	Complex profiles used for structural stiffeners and rails
Tube	0.5–8.0 mm wall	Good axial strength; bending/forming depends on temper	O, T6	Used for lightweight structural tubing and aerospace systems
Bar/Rod	Ø5–100 mm	Strength varies with diameter and heat treatment	O, T6	Used for fittings, machined components and fasteners

Sheet and thin‑gauge products are widely used for 8007 because they achieve more consistent quench and aging responses and better formability in O and H tempers. Plate and large‑cross‑section extrusions require careful control of solution treatment and quenching to avoid soft center zones and to obtain uniform mechanical properties.

Processing differences (rolling vs extrusion) influence texture, anisotropy and formability. Where tight property uniformity is required across thickness, suppliers may specify solution and temperature control or prefer cold‑worked tempers combined with controlled aging.

Equivalent Grades

Standard	Grade	Region	Notes
AA	8007	USA	Common industry designation for this chemistry family; supplier variations exist
EN AW	8xxx (various)	Europe	EN standards typically group Li‑bearing alloys under 8xxx designations; direct mapping depends on exact chem
JIS	A8xxx series	Japan	Japanese standards have analogous 8xxx family entries; grade number varies with chemistry
GB/T	8007 (or 8xxx series)	China	Chinese standards often use series-based numbering; exact equivalents require composition check

Exact equivalents for 8007 are not always one‑to‑one due to proprietary variations and narrow composition windows used by suppliers. Engineers should request certified chemical and mechanical test reports and, when necessary, compare specific limits for Li, Cu and Mg to confirm equivalence across standards.

Corrosion Resistance

Atmospheric corrosion resistance of 8007 is generally good for Li‑bearing alloys when Cu and Zn contents are controlled; protective alumina forms naturally, and appropriate tempering and surface finish improve performance. However, higher Cu or Zn levels increase susceptibility to pitting and exfoliation in aggressive environments, so specification must be tailored for service conditions.

In marine and chloride‑rich environments 8007 performs acceptably when compared to 2xxx series alloys but may be less robust than pure Al‑Mg alloys (5xxx) unless inhibitors, coatings or protective treatments are used. Attention to alloy temper and post‑weld treatments is necessary to mitigate localized attack, especially around fasteners and joins.

Stress corrosion cracking risks increase with tensile stress and with certain chemistries (notably higher Cu); judicious design to reduce sustained tensile stress and the use of corrosion‑resistant tempers and coatings mitigates this risk. Galvanic interactions place 8007 on the anodic side relative to common stainless steels and copper alloys; insulating interfaces or selecting compatible fasteners is recommended.

Compared with other families, 8007 typically offers better specific stiffness and comparable or improved corrosion resistance versus high‑strength Al‑Cu alloys, but it rarely matches the pure corrosion robustness of 5xxx Mg‑alloys in uncoated marine exposures.

Fabrication Properties

Weldability

Welding 8007 using GTAW (TIG) and GMAW (MIG) is feasible but requires process control to limit Li vaporization and to manage HAZ softening. Typical filler alloys are Al‑Si or Al‑Mg‑Si types selected to balance strength and corrosion behavior, and preheat/controlled post‑weld solution treatment or mechanical stress relief may be needed for critical structures. Hot‑cracking risk is moderate and increases with higher Cu/Zn; pulsed welding and vacuum or inert shielding for critical aerospace parts are common practices.

Machinability

Machinability of 8007 is fair to good depending on temper and section size; higher strength tempers reduce machinability due to increased work‑hardening and tool loading. Carbide tooling with positive rake and good chip evacuation is recommended; cutting speeds are typically higher than steel but lower than pure aluminum due to alloying. Chip formation tends toward short segmented chips with adequate feed and lubrication; coolant and chip control improve surface finish and extend tool life.

Formability

Formability is excellent in O and lightly worked H tempers and degrades in peak‑aged T6/T8 conditions where elongation and bendability fall. Typical minimum bend radii in O temper are small (R/t ≈ 1–2) depending on temper and tooling, whereas T6 may require larger radii and more springback compensation. Warm forming and solution treat/age cycles are used to improve formability for complex shapes followed by artificial aging to regain strength.

Heat Treatment Behavior

As a heat‑treatable alloy, 8007 undergoes classical solution treatment, quenching and artificial aging cycles to develop peak strength. Solution treatment temperatures are typically in the range of 500–540 °C depending on exact chemistry; uniform quenching is critical to suppress coarse precipitate formation and to retain solute supersaturation for subsequent aging.

Artificial aging is performed at moderate temperatures (typically 120–180 °C) to nucleate and grow fine δ' (Al3Li) precipitates that confer high strength and stiffness. Overaging at higher temperatures or prolonged times leads to coarsening of precipitates and loss of peak properties; temper selection (T6 vs T8/T91) manages trade‑offs between strength and toughness.

Tempering transitions include natural aging in some tempers (T3) where partial precipitation occurs at room temperature, and cold work followed by aging (T8) where dislocation networks aid heterogeneous nucleation giving higher yield strengths. Control of cooling rates and aging cycles is essential to avoid property gradients, particularly in thick sections or complex assemblies.

High-Temperature Performance

8007 exhibits a notable reduction in strength above approximately 125–150 °C as Li‑containing precipitates begin to coarsen and dissolve, limiting continuous service temperatures. Short‑term exposures up to ~200 °C may be tolerated depending on temper and required properties, but long‑term elevated temperature service is not recommended for load‑bearing applications.

Oxidation under ambient conditions is limited since aluminum forms a protective oxide layer, but at high temperatures surface scaling and changes in surface chemistry can occur. HAZ during welding is an area of concern: localized softening and loss of tensile properties are typical due to precipitate dissolution and re‑precipitation; post‑weld heat treatments or mechanical stress relief are commonly specified for critical parts.

Creep resistance of 8007 is limited compared with high‑temperature alloys; designers should avoid prolonged stresses at elevated temperatures and should perform application‑specific testing when thermal excursions are expected.

Applications

Industry	Example Component	Why 8007 Is Used
Aerospace	Fuselage stiffeners, internal fittings	High specific stiffness and reduced weight for structural efficiency
Marine	Lightweight superstructure panels	Lower density and good strength with controlled corrosion behavior
Automotive	Structural reinforcements, crash management parts	Weight reduction for fuel economy while retaining required strength
Electronics	Heat spreaders and housings	Lower mass and acceptable thermal conductivity with structural integrity

8007 is chosen where mass savings and increased stiffness are design drivers while retaining the ability to reach moderate to high strengths through heat treatment. The alloy’s combination of properties suits applications where both structural performance and weight savings yield system‑level benefits, such as aerospace primary and secondary structures, high‑end transport components and certain thermal management parts.

Selection Insights

When selecting 8007, prioritize use cases that require improved specific stiffness and reduced mass but still demand moderate to high strength achievable through aging. Specify tempering and post‑fabrication treatments early to avoid surprises in formability, weld performance and corrosion behavior.

Compared with commercially pure aluminum (e.g., 1100), 8007 trades some electrical and thermal conductivity and formability for much higher strength and lower density, making it a preferred choice for structural components rather than pure conductive or highly formable applications. Compared with common work‑hardened alloys (e.g., 3003, 5052), 8007 offers superior specific strength and stiffness at the cost of reduced ductility in peak tempers and potentially higher material cost. Compared with common heat‑treatable alloys (e.g., 6061/6063), 8007 can be chosen when the priority is lowest density and higher specific stiffness even if peak absolute strength may be similar or slightly lower; choose 8007 where weight saving and modulus per unit mass are decisive.

Closing Summary

Aluminum alloy 8007 remains relevant where designers demand a combination of reduced density, increased specific stiffness and heat‑treatable strength, particularly in aerospace and weight‑sensitive transportation sectors. Proper specification of chemistry, temper and fabrication sequence unlocks its advantages while managing trade‑offs in formability, weldability and corrosion behavior.