Aluminum 5456: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

5456 is a member of the 5xxx series aluminum–magnesium alloys, characterized by moderate-to-high magnesium content and non-heat-treatable strengthening. The alloy sits among higher-magnesium variants used where strength and corrosion resistance must be balanced with good weldability and reasonable formability.

Primary alloying is magnesium in the ~4.7–5.7 wt% range with controlled manganese and chromium additions to refine grain structure and improve strength and resistance to recrystallization. Strength is developed principally by solid-solution strengthening from Mg and by strain hardening; it is not responsive to precipitation heat treatments in the way 6xxx or 7xxx series alloys are.

Key traits include higher yield and tensile strength than lower-Mg 5xxx alloys, very good resistance to general and localized corrosion in marine atmospheres when properly processed, and good weldability with appropriate filler metals. Formability is adequate in annealed tempers but diminishes as the alloy is strain hardened; this trade-off guides temper selection for forming vs structural use.

Typical industries include shipbuilding, offshore structures, pressure vessels, railcars, and automotive extrusions where the combination of strength-to-weight and corrosion resistance is required. Engineers select 5456 over other alloys when a non-heat-treatable alloy with higher intrinsic strength and marine-grade corrosion performance is needed without the complexity of heat-treatment processing.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (≥20–30%)	Excellent	Excellent	Fully annealed, best for deep drawing and forming
H111	Medium	Moderate (≈15–25%)	Good	Excellent	Slightly strain-hardened, non-stabilized, general-purpose
H112	Medium	Moderate	Good	Excellent	Commercially produced with directionality control
H32	High	Lower (≈8–15%)	Reduced	Excellent	Strain-hardened and stabilized, commonly used for structural parts
H34	High	Lower	Reduced	Excellent	Higher work-hardening level for strength-critical parts
H116	High	Moderate	Good	Excellent	Stabilized for improved resistance to marine SCC and intergranular corrosion
H321	Medium-High	Moderate	Good	Excellent	Thermally stabilized after cold work to resist sensitization

Temper strongly controls the balance of strength, ductility and formability in 5456. Annealed (O) temper is used where forming operations dominate and peak strength is unnecessary, while H3x/H1xx series tempers provide progressively higher strength by cold work at the cost of elongation and stretch-forming capacity.

Stabilized tempers (H116, H321) use tight control of trace elements and/or light thermal stabilization to reduce susceptibility to localized corrosion and stress-corrosion cracking in chloride environments. Selection of temper must consider final part geometry, required strength margins, and post-weld requirements.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.25	Impurity control; higher Si reduces ductility and may form brittle intermetallics
Fe	≤ 0.40	Common impurity; excess promotes intermetallic particles that can affect strength and corrosion
Mn	0.20–0.70	Grain refiner and strengthening element; improves ductility and resistance to recrystallization
Mg	4.7–5.7	Primary strengthening element; increases strength and corrosion resistance but raises SCC risk if uncontrolled
Cu	≤ 0.10	Kept low to preserve corrosion resistance; higher Cu increases strength but reduces marine performance
Zn	≤ 0.25	Minor; excessive Zn can reduce corrosion resistance
Cr	0.05–0.25	Controls grain growth and improves resistance to recrystallization and stress corrosion
Ti	≤ 0.10	Grain refiner when present in small amounts
Others (each)	≤ 0.05	Total others ≤ 0.15; kept low to avoid deleterious phases

Magnesium is the dominant micro-alloying agent, providing solid solution strengthening and improving strength-to-weight ratio. Manganese and chromium are purposeful microalloying elements that counteract grain growth during thermomechanical processing and stabilize the microstructure against excessive texture and recrystallization.

Tight control of copper, iron and silicon is essential for marine-grade performance; trace impurities and intermetallic particles influence pitting initiation sites and localized electrochemical behavior. The final performance is therefore a function of nominal composition and processing history, including rolling, solutionizing (if used), and stabilizing treatments.

Mechanical Properties

Tensile behavior of 5456 is strongly temper-dependent: annealed material exhibits high elongation and modest tensile strength, while H3x/H1xx tempers show substantially increased yield and ultimate strength due to cold work. Yield-to-tensile ratios are typically tighter in cold-worked tempers, which aids design predictability for thin-walled structure but reduces forming window and necessitates careful control of bend radii.

Hardness correlates with temper and Mg content; the hardness range spans from low Vickers in O-temper to significantly higher levels in H32/H34 types. Fatigue performance is generally good for aluminum alloys of this class, but fatigue crack initiation can be sensitive to surface condition, residual stresses from forming or welding, and the presence of intermetallic particles.

Thickness and section size influence properties through work-hardening behavior and grain structure control; thicker plate can show slightly higher yield at similar nominal tempers due to constraint during rolling. Welding produces a heat-affected zone with partial softening in heavily strain-hardened temper conditions and designers must account for HAZ reduction in strength.

Property	O/Annealed	Key Temper (H32 / H116)	Notes
Tensile Strength (UTS)	~140–190 MPa	~270–340 MPa	Range dependent on thickness and exact temper; cold work increases UTS substantially
Yield Strength (0.2% offset)	~35–80 MPa	~200–300 MPa	H32/H116 offer much higher yield useful for structural design; values vary with sheet thickness
Elongation (in 50 mm)	~20–35%	~8–18%	Ductility reduced by work hardening; annealed condition best for forming
Hardness (HV)	~30–45 HV	~75–110 HV	Indicative values; hardness correlates with temper and cold work level

Physical Properties

Property	Value	Notes
Density	2.66 g/cm³	Typical aluminum alloy density; used in mass and strength-to-weight calculations
Melting Range	~570–640 °C	Solidus-to-liquidus range depends slightly on alloying; avoid service near melting range
Thermal Conductivity	~120–140 W/(m·K)	Lower than pure aluminium but still high; beneficial for heat-dissipation applications
Electrical Conductivity	~28–34 % IACS	Reduced compared with pure Al; conductivity decreases with Mg and alloying additions
Specific Heat	~900 J/(kg·K)	Typical for Al alloys at ambient temperatures
Thermal Expansion	~23–24 µm/(m·K)	Coefficient similar to most aluminium alloys; important for thermal cycle design

Density and thermal properties make 5456 attractive where weight and heat dissipation are design drivers. Thermal conductivity and specific heat remain high compared to ferrous metals, enabling efficient passive cooling in structural heat-sinking applications.

Electrical conductivity is lower than commercially pure aluminium but remains adequate for many electrical and thermal conduction roles; design must consider conductivity loss with alloying as part of EMI/thermal path calculations. Thermal expansion is typical for aluminum and must be accommodated in multi-material assemblies.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6.0 mm	Strength varies strongly with temper; thinner gauges are easier to cold-form	O, H111, H32, H116	Widely used for panels and formed components
Plate	6–200 mm	Thick plates develop slightly higher through-thickness strength; rolling history important	H32, H116	Structural and marine hull plates; heavy gauge requires controlled rolling
Extrusion	Variable cross-sections	Strength depends on downstream ageing and cold work; extrusions may be stress relieved	O, H112, H32	Complex profiles for chassis and structural frames
Tube	Diameters up to several hundred mm	Strength and collapse resistance controlled by wall thickness and temper	O, H32	Pressure and structural tubing; welding and bending considered
Bar/Rod	Up to several inches diameter	Often supplied in partially cold-worked tempers; machinability varies	O, H111	Fasteners, pins and machined components; section size affects final properties

Sheets and plates are produced by rolling and can be supplied in many tempers to meet forming or structural needs; control of rolling schedule and cooling is critical to achieve targeted mechanical properties. Extrusions and tubes rely on downstream processing and age/stabilization cycles to prevent later dimensional instability and to manage anisotropy.

Formed components typically begin in O or light H1xx tempers when extensive forming is required, then may be cold worked or stabilized to reach final mechanical requirements. Plates used in marine or structural applications are often produced in stabilized H116 to minimize susceptibility to localized corrosion and SCC.

Equivalent Grades

Standard	Grade	Region	Notes
AA	5456	USA	Original Aluminum Association designation commonly used in specification sheets
EN AW	5456	Europe	EN AW-5456 exists in European standards as the same nominal composition with regional tolerances
JIS	A5456 (or similar)	Japan	Local standard designation used for equivalent 5xxx high-Mg alloys; check JIS catalog for exact match
GB/T	5456	China	Chinese GB/T designation aligns ordinarily with AA 5456 but manufacturing tolerances and tempers can differ

Cross-standard equivalence generally holds at the nominal composition level, but differences arise in accepted impurity limits, required mechanical test thicknesses, and temper designations. Regional standards may also specify different acceptable tempers or additional stabilization requirements for marine service.

Engineers should always compare the full standards text for chemical and mechanical tolerances, agreed test methods, and specified certification (e.g., mill test reports) when substituting across standards to ensure functional parity.

Corrosion Resistance

5456 exhibits very good resistance to general atmospheric and seawater corrosion compared with many heat-treatable aluminum alloys, owing largely to the beneficial effects of magnesium in promoting protective surface films. In mildly corrosive atmospheres the alloy performs well, and with controlled impurities and stable tempers it is widely accepted for marine hulls and offshore structures.

However, high magnesium content increases susceptibility to localized attack and stress-corrosion cracking (SCC) in chloride-containing environments unless the alloy is produced and stabilized for marine service. Stabilized tempers (H116, H321) and low-copper chemistries mitigate SCC risk by limiting intermetallics and sensitization effects.

Galvanic interactions with cathodic materials such as stainless steel or copper must be managed by insulating layers or using compatible fasteners; aluminum alloys like 5456 will be anodic in many bimetallic couples and can corrode preferentially if in electrical contact in an electrolyte. Compared with 6xxx series (Al–Mg–Si) or 7xxx series (Al–Zn), 5456 provides superior general and marine corrosion resistance but is more prone to chloride-induced SCC than lower-Mg 5xxx alloys with tighter impurity limits.

Fabrication Properties

Weldability

5456 welds readily using common fusion processes such as GTAW (TIG) and GMAW (MIG), and it is tolerant of high-heat inputs without hot cracking when fillers are chosen correctly. Aluminum–magnesium filler alloys such as ER5356 or ER5183 are commonly recommended to match strength and maintain corrosion resistance in the weld deposit and HAZ. The HAZ can experience softening if base material is strain-hardened; post-weld mechanical properties must be assessed and, when necessary, localized tempering or design adjustments applied.

Machinability

Machining 5456 is moderate compared to free-machining alloys; its relatively high Mg increases strength and work hardening, which can blunt cutting edges faster than near-pure alloys. Carbide tooling with positive rake, adequate coolant, and controlled chip evacuation are recommended to manage built-up edge and reduce work hardening effects. Feed rates and speeds should be tuned for section size and temper; lighter cuts and interrupted cutting strategies help with thicker, work-hardened sections.

Formability

Formability is excellent in the annealed condition but falls as cold work increases; minimum inside bend radii for sheet are typically governed by temper and thickness and should be validated by forming trials. For stretch forming and deep drawing, O temper or very light H1xx tempers are preferred, while H32/H34 parts are better suited to operations requiring final dimensional stability with less forming. Springback is greater in higher-strength tempers and must be accounted for in die design and tool offsets.

Heat Treatment Behavior

Being a non-heat-treatable alloy, 5456 does not respond to precipitation hardening to raise strength; instead, strength increases come from work hardening and cold deformation. Annealing (O) is performed at elevated temperatures to restore ductility by recrystallization; the process parameters vary with thickness but typically involve temperatures in the 300–400 °C range followed by controlled cooling.

Thermal stabilization treatments (designated H116/H321 in practice) use modest thermal exposure or tight composition control to minimize susceptibility to intergranular corrosion and stress-corrosion cracking. These stabilization steps are not aimed at producing additional strength but at setting a more corrosion-stable microstructure and relieving residual stresses after cold work.

Because there is no T6-like strengthening path, engineers seeking higher strength rely on thermo-mechanical processing, controlled cold work, and selection of the highest practical H3x temper consistent with formability and welding demands. Over-tempering or exposure to elevated temperatures during service or welding can reduce cold-worked strength by recovery and partial recrystallization.

High-Temperature Performance

5456 retains useful mechanical properties at moderate elevated temperatures but experiences progressive strength loss as temperature rises above ambient, with significant reductions typically above 150–200 °C. Creep resistance is limited compared with specialized, high-temperature alloys; long-term loading at elevated temperatures is not recommended without specific testing.

Oxidation in air is minimal due to the formation of protective oxide films; however, elevated temperatures can accelerate diffusion processes that reduce cold-work strength and can alter surface finish or dimensional stability. In welded structures, the HAZ is often the weak link at elevated temperatures because microstructural recovery and softening can be accelerated by subsequent thermal cycles.

Designers should limit continuous service temperatures and consider thermal cycling effects on fatigue life and residual stress redistribution. For short-term exposure to higher temperatures, 5456 can be acceptable, but long-term structural applications at high temperature require alternate alloys or protective design measures.

Applications

Industry	Example Component	Why 5456 Is Used
Marine	Hull plate, superstructure panels	High corrosion resistance in seawater and good strength for welded structures
Offshore / Energy	Platform components, piping supports	Strength and weldability in large structural sections with chloride exposure
Automotive / Transportation	Trailer panels, structural sections	High strength-to-weight and good dent resistance for body and chassis components
Aerospace	Secondary structures, fittings	Strength and fracture resistance where non-heat-treatable alloys are preferred
Electronics / Thermal	Heat spreaders, frames	High thermal conductivity and low density for passive cooling

5456 is widely specified where a combination of high Mg-enabled strength, good weldability and marine corrosion resistance are needed in structural forms. Its balance of properties makes it a common choice for heavy-gauge panels, welded structures and components that must remain corrosion-resistant without requiring precipitation hardening.

Selection Insights

5456 is a good choice when engineers need a non-heat-treatable aluminum with greater strength than commercially pure alloys while maintaining excellent marine corrosion resistance. Compared with 1100, 5456 trades off some electrical conductivity and formability for substantially higher yield and tensile strength.

Against work-hardened alloys such as 3003 or 5052, 5456 generally offers higher strength and better performance in seawater, though it can be more prone to chloride SCC unless supplied in stabilized tempers like H116. Compared with heat-treatable alloys such as 6061 or 6063, 5456 provides superior corrosion resistance and easier welding but lower peak strength; choose 5456 when corrosion and weld integrity outweigh the need for maximum attainable strength.

For procurement and design, prioritize temper selection (O vs H32 vs H116) according to forming needs and service environment, confirm filler compatibility for welding, and specify stabilization if marine SCC is a concern. Cost and availability are generally favorable for 5xxx alloys, but confirm local millstock tempers and plate thickness options early in the design phase.

Closing Summary

5456 remains a relevant engineering alloy because it combines elevated magnesium-driven strength with strong marine corrosion resistance and straightforward weldability, serving structural and marine markets where heat treatment is impractical. Its predictable temper-dependent behavior and availability in plate, sheet and extruded forms make it a practical choice for designers balancing strength, durability and manufacturability.