Aluminum 5086: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

5086 is part of the 5xxx series of wrought aluminum–magnesium alloys, categorized by magnesium as the principal alloying element. This series is non-heat-treatable and derives its strength primarily from solid-solution strengthening and work hardening rather than precipitation hardening.

Major alloying content in 5086 includes magnesium at several weight percent plus small additions of chromium and trace elements that control grain structure and corrosion behavior. The alloy is strengthened by cold working (strain hardening) and by a carefully controlled alloy chemistry that balances strength with corrosion resistance in chloride environments.

Key traits of 5086 are relatively high strength for an aluminum sheet alloy, excellent marine corrosion resistance, good weldability, and reasonable formability in softer tempers. These attributes make it a common choice for ship hulls, pressure vessels, cryogenic tanks, and structural components where a combination of toughness, corrosion resistance, and weldability is required.

Engineers choose 5086 over other alloys when marine or chloride-containing environments demand superior resistance to pitting and stress-corrosion cracking while retaining a favorable strength-to-weight ratio. It is selected over heat-treatable alloys when post-weld properties and resistance to localized corrosion take precedence over absolute peak strength.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; maximum ductility for forming
H111	Low–Moderate	High	Very Good	Excellent	Slightly work-hardened; general-purpose temper
H32	Moderate	Good	Good	Very Good	Strain-hardened and stabilized; balanced strength and formability
H34	Moderate–High	Moderate	Fair–Good	Very Good	Higher work hardening than H32 for elevated strength
H116	Moderate–High	Moderate	Fair	Very Good	Stabilized for superior marine performance, commonly supplied for welded marine structures

Tempers for 5086 are achieved by controlled cold working and stabilization rather than by solution and precipitation heat treatment. Moving from O to progressively higher H tempers increases strength and reduces ductility; this changes forming strategies and limits minimum bend radii.

Selected tempers such as H116 are designed to limit strain aging and to maintain corrosion resistance after welding and exposure to marine environments. Design and fabrication must account for H-temper reductions in formability and the possibility of springback and anisotropic properties in heavily worked material.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.40	Impurity; controlled to avoid intermetallics that reduce toughness
Fe	≤ 0.50	Impurity; excessive Fe can form brittle intermetallics
Mn	0.05–0.50	Small additions aid strength and grain structure control
Mg	3.5–4.9	Principal strengthening element; improves corrosion resistance
Cu	≤ 0.10	Minimized to retain corrosion resistance
Zn	≤ 0.25	Low to avoid embrittlement and corrosion susceptibility
Cr	0.05–0.25	Grain structure control, improves recrystallization resistance
Ti	≤ 0.15	Grain refiner in some cast/ingot practices
Others (each)	≤ 0.05	Traces and residual elements; Al balance

The Mg content in 5086 is the dominant factor controlling strength and corrosion resistance: higher Mg increases strength and pitting resistance but can raise susceptibility to stress-corrosion cracking if unbalanced. Chromium is intentionally present at low levels to control grain growth, particularly during thermal cycles such as welding, which improves toughness and reduces exfoliation. Low copper and zinc levels preserve resistance to localized corrosion in seawater.

Mechanical Properties

5086 exhibits a tensile behavior typical of non-heat-treatable Al–Mg alloys: ductile tensile failure with considerable plasticity in annealed tempers and progressively higher yield strength with strain hardening. The alloy shows good notch toughness and retains energy-absorption capability at low temperatures, which is why it is often used in cryogenic vessels.

Yield and tensile strengths depend strongly on temper and cold work; thicker sections and welded heat-affected zones (HAZ) may exhibit softened regions due to thermal exposure. Fatigue performance is generally good in well-finished, corrosion-protected specimens, but corrosion pits and weld defects dramatically reduce fatigue life.

Hardness correlates with strength; typical Brinell or Vickers hardness rises with H tempering. Designers must account for thickness effects: thin sheet is easier to cold work to higher strength levels, while thick plate is more limited in achievable cold work without cracking.

Property	O/Annealed	Key Temper (e.g., H116/H32)	Notes
Tensile Strength	200–260 MPa (29–38 ksi)	300–370 MPa (44–54 ksi)	Values vary by thickness, supplier and exact temper; H tempers give significantly higher UTS
Yield Strength	85–150 MPa (12–22 ksi)	210–260 MPa (30–38 ksi)	Yield increases markedly with cold work and stabilization
Elongation	12–25%	6–16%	Annealed is highly ductile; H tempers trade ductility for strength
Hardness	~35–65 HB	~80–95 HB	Hardness increases with strain hardening and correlates with tensile/yield strengths

Physical Properties

Property	Value	Notes
Density	2.66 g/cm³	Typical density for Al–Mg wrought alloys; good strength-to-weight ratio
Melting Range	Solidus ~565–600 °C, Liquidus ~635–650 °C	Alloy melting ranges depend on minor constituents and segregation
Thermal Conductivity	~120–140 W/m·K	Lower than pure Al but still high; useful for thermal management
Electrical Conductivity	~28–36 %IACS	Reduced relative to pure Al due to alloying; conductive enough for many applications
Specific Heat	~0.90 J/g·K	Similar to other Al alloys; useful for thermal mass calculations
Thermal Expansion	~23–24 ×10⁻⁶ /K (20–100 °C)	Standard aluminum expansion; important for multi-material joins

The alloy's density and thermal properties contribute to its common selection for lightweight structures where thermal conductivity and heat dissipation are required, such as decks, heat exchangers, and cryogenic tanks. Thermal expansion requires design consideration when mating 5086 to dissimilar materials such as steel or composites to avoid differential thermal stresses.

Electrical and thermal conductivities are moderated by the Mg and trace element content but remain high enough for many conductive applications. The melting range and solidus/liquidus behavior are important for welding parameters and for determining thermal cycles that might cause overaging or softening in H-temper materials.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Uniform thin-section behavior; easy to cold work	O, H111, H32	Widely used for hull plating, panels
Plate	6–150+ mm	Thicker sections have lower cold-workability; require more pre- and post-processing	O, H116, H34	Structural members, pressure vessel plates
Extrusion	Profiles up to large cross-sections	Mechanical properties influenced by extrusion and subsequent cold work	O, H32	Complex profiles for frames and structural rails
Tube	Thin- to thick-walled diameters	Performance depends on forming/welding method	O, H32	Marine piping and structural tubing
Bar/Rod	Diameters up to large sections	Bars provide machinability and mechanical stability	O, H32	Fittings, machined components

Processing differences affect final properties: sheet and thin plate are amenable to high levels of cold work to reach H tempers, whereas thick plate is limited and may be supplied in softer tempers or require mechanical forming approaches. Extrusions and tubes require careful control of quench and stabilization to preserve desired mechanical and corrosion performance.

Applications differ by product form: sheet and plate dominate marine hull construction, extrusions enable complex structural shapes and rails, and tube and bar forms are commonly used for fittings and welded assemblies. Suppliers often offer pre-stabilized tempers for welded structures to improve HAZ performance.

Equivalent Grades

Standard	Grade	Region	Notes
AA	5086	USA	Aluminum Association designation; common commercial reference
EN AW	5086	Europe	EN AW-5086 matches AA composition and tempers with regional manufacturing tolerances
JIS	A5086	Japan	Similar chemistry; JIS covers typical tempers and manufacturing practices
GB/T	AlMg4.5Mn (or 5086)	China	Local designation may reference magnesium content (e.g., AlMg4.5) with similar temper options

Standards in different regions align on the core chemistry and intended performance but can differ in allowable impurity limits, required mechanical testing, and temper definitions. Buyers should check sheet/plate certificates and temper codes when sourcing internationally to ensure HAZ, corrosion, and mechanical expectations are met.

Traceability to a recognized standard (AA, EN, JIS, GB/T) is particularly important for safety-critical applications like marine structural plating and pressure vessels, where small differences in composition or temper can affect long-term corrosion or fracture behavior.

Corrosion Resistance

5086 shows excellent atmospheric corrosion resistance and is among the preferred wrought alloys for seawater contact due to its high magnesium content and low copper/zinc content. In marine environments the alloy resists general corrosion and demonstrates good pitting resistance compared with many other aluminum alloys.

In long-term immersion and splash-zone exposure, 5086 performs well provided designs avoid stagnant crevices, poorly drained joints, and dissimilar-metal contact that can set up galvanic cells. The alloy is less prone to exfoliation than some high-strength 7xxx series alloys, but careful detailing and protective coatings extend service life.

Stress corrosion cracking (SCC) susceptibility is lower than for higher-Mg or certain heat-treatable alloys, but SCC can still occur under tensile stresses, elevated temperatures, or in high-chloride environments if microstructural conditions are unfavorable. Galvanic interactions with cathodic materials (e.g., copper, stainless steels as cathodes) can accelerate localized attack; insulation or sacrificial anode design is recommended.

Compared with 3xxx and 1xxx series alloys, 5086 offers superior strength and comparable or better corrosion resistance in seawater. Compared with 6xxx and 7xxx families, 5086 sacrifices some peak strength but gains significantly in marine corrosion performance and weldability.

Fabrication Properties

Weldability

5086 welds readily with common fusion methods (GMAW/MIG, GTAW/TIG, and resistance welding) and shows good bead appearance and fusion when joint fit-up and parameters are controlled. Use of matching or slightly overstrength filler alloys (e.g., 5183, 5356) is recommended; filler selection balances weld strength, ductility and corrosion performance.

Weld heat-affected zones can exhibit softening if base metal is in a high H temper; stabilized tempers such as H116 are specified to limit post-weld sensitivity. Hot-cracking risk is low compared with certain high-strength Al alloys but inclusion control and clean surfaces are essential for reliable welds.

Machinability

5086 has moderate machinability compared with other wrought alloys; it machines better than many high-Mg cast alloys but worse than 6xxx series aluminum containing silicon for chip control. Use sharp carbide tooling, rigid setups, and moderate-to-high feed rates to avoid tool rubbing and work hardening.

Cutting speeds and feeds should be tuned to section thickness and temper; H-tempers increase work-hardening tendency and may produce longer continuous chips. Coolant is recommended to clear chips and reduce heat buildup; surface finish improves with fine passes and controlled tool geometry.

Formability

Formability is excellent in O and H111 tempers and degrades as the alloy is strain hardened to H32/H34/H116 conditions. Minimum bend radii depend on temper and thickness; annealed sheet can take tight radii (≈1–2× thickness), whereas H tempers often require larger radii and multi-step forming sequences.

Cold forming and incremental bending are common; for complex shapes consider warm forming or pre-anneal cycles to reduce springback and cracking. The alloy responds predictably to controlled stretch forming but localized thinning can occur in deep draws if blank holder pressure and lubrication are not optimized.

Heat Treatment Behavior

As a member of the 5xxx series, 5086 is non-heat-treatable in the precipitation-hardening sense; solution treatment and artificial aging do not substantially raise strength. Attempts to thermally age the alloy will mainly affect recovery and recrystallization rather than produce significant strengthening precipitates.

The primary means of increasing strength is work hardening by cold deformation followed by stabilization treatments (e.g., H116) to minimize strain aging and microstructural changes during service. Annealing (O) returns the material to a low-strength, high-ductility condition and is used to restore formability after heavy working.

Thermal exposure from welding can locally anneal cold-worked regions and reduce yield and hardness in H tempers; post-weld mechanical processing or design selection of stabilized tempers is the common mitigation path. Controlled bake cycles are sometimes used to relieve residual stresses but will not produce peak precipitate hardening as in 6xxx/7xxx alloys.

High-Temperature Performance

5086 loses strength progressively with increasing temperature; useful design strength is typically specified for ambient to moderately elevated temperatures (up to ~100 °C). For continuous service above ~100–150 °C, strength and creep resistance fall off, and designers should consult specific elevated-temperature data for the application.

Oxidation is limited to a stable aluminum oxide film, so high-temperature surface degradation in air is minimal compared with ferrous alloys. However, thermal exposure can change microstructure in H-tempers, reduce residual cold work, and increase susceptibility to localized corrosion in aggressive environments.

Weld HAZs exposed to repeated thermal cycling may experience microstructural coarsening and softening; structural applications subjected to high heat loads or repeated thermal excursions require careful qualification and sometimes alternative alloy selection.

Applications

Industry	Example Component	Why 5086 Is Used
Marine	Hull plating, superstructure	Excellent seawater corrosion resistance and good weldability
Automotive	Bulkheads, fuel tanks	Good strength-to-weight and dent/impact resistance
Aerospace	Non-critical fittings, fairings	High toughness and corrosion resistance where extreme peak strength is not required
Energy / Cryogenics	LNG tanks, cryogenic vessels	Toughness at low temperature and weldability
Industrial / Pressure vessels	Chemical tanks, storage vessels	Corrosion resistance to many chemicals and favorable forming

5086 is a workhorse alloy where designers need a balance of weldability, corrosion resistance and moderate-to-high strength without relying on precipitation hardening. It is especially valuable where welded joints will see marine exposure or where post-weld mechanical properties are critical.

Selection Insights

Choose 5086 when marine corrosion resistance and weldability are prioritized over absolute peak strength; it is a practical choice for hulls, tanks, and welded structures. The stabilized H116 temper is often specified where post-weld corrosion resistance and dimensional stability are required.

Compared with commercially pure aluminum (1100), 5086 trades higher strength and better seawater performance for somewhat reduced electrical conductivity and marginally lower formability. Compared with common work‑hardened alloys such as 3003 or 5052, 5086 provides higher strength and comparable or better chloride corrosion resistance, making it preferable in aggressive maritime environments.

Compared with heat-treatable alloys such as 6061 or 6063, 5086 offers superior corrosion behavior and weldability though lower maximum achievable strength; choose 5086 when corrosion and post-weld performance matter more than maximizing tensile/yield properties. For designs needing higher strength, consider structural choices that