Aluminum 535: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

Aluminum alloy 535 is a member of the 5xxx series of wrought aluminum-magnesium alloys characterized by magnesium as the principal alloying element. The 5xx series are non-heat-treatable and rely primarily on solid-solution strengthening and strain-hardening to achieve elevated mechanical properties, with minor additions such as manganese and chromium used to control grain structure and improve corrosion resistance.

The dominant alloying element in 535 is magnesium in the mid single-digit percent range, supported by small levels of manganese and trace elements that refine microstructure and influence work-hardening response. Key traits include good medium-to-high strength for a non-heat-treatable alloy, robust general and marine corrosion resistance, favorable weldability with some filler choices, and good cold formability in annealed conditions.

Industries that commonly employ 535 include marine and shipbuilding, transportation and automotive structures where weight savings and corrosion resistance are important, as well as general fabrication for pressure vessels and architectural panels. The alloy is chosen when designers need a combination of greater strength than pure aluminum and excellent environmental durability without the complexity or cost of heat treatment operations.

Compared to heat-treatable alloys, 535 avoids solution and aging cycles and maintains stable properties after welding and long-term service in chloride-bearing atmospheres. Its selection is frequently driven by the balance of strength, weld-ability, and cost where moderate-to-high static strength and good fatigue resistance under corrosive conditions are required.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (18–25%)	Excellent	Excellent	Fully annealed condition for forming and deep drawing
H111 / H112	Medium-Low	Medium-High (12–18%)	Very good	Very good	Slightly strain-hardened, general-purpose temper
H14 / H18	Medium	Medium (8–14%)	Good	Good	Commercially hardened to moderate strength
H22 / H24	Medium-High	Medium (8–12%)	Acceptable	Good	Higher work-hardening for structural parts
H32 / H116	High	Lower (6–12%)	Limited	Good	Stabilized or strain-relieved for welded/marine service
T5 / T6 / T651	Not applicable / Uncommon	Variable	Variable	Variable	Heat-treatment designations are not used for 5xxx series; listed for reference only

The temper selected for 535 directly controls the interplay between strength and ductility: annealed (O) tempers maximize formability while H temper levels progressively increase yield and tensile strength at the expense of elongation. Marine-grade stabilizations such as H116 or H321 are employed to minimize post-weld softening and to provide consistent behavior in welded structures.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.25	Kept low to avoid deleterious intermetallics, improves casting compatibility
Fe	≤ 0.50	Impurity element; excessive Fe forms brittle intermetallics that can harm ductility
Mn	0.3–1.0	Grain refiner; improves strength and reduces susceptibility to localized corrosion
Mg	3.0–4.5	Principal strengthening element; enhances strength and corrosion resistance
Cu	≤ 0.10	Kept minimal to preserve corrosion resistance and minimize SCC risk
Zn	≤ 0.25	Low levels tolerated; higher Zn can reduce corrosion resistance
Cr	0.05–0.25	Controls grain structure and improves strength stability during thermal exposure
Ti	≤ 0.10	Trace addition for grain refinement in cast or large-section products
Others	Balance Al	Aluminum is the remainder with trace allowable elements per specification

The moderate magnesium level is the primary driver of solid-solution strengthening in 535 and enhances anodic corrosion resistance, particularly in chloride environments. Manganese and chromium act as microstructure stabilizers that prevent excessive grain growth during fabrication and welding, maintaining toughness and reducing susceptibility to intergranular corrosion.

Mechanical Properties

Tensile behavior for 535 shows a strong dependence on temper and processing history. In the annealed O condition the alloy exhibits high ductility and moderate tensile strength, enabling deep drawing and complex forming operations. Strain-hardening to H-temper levels increases yield strength markedly while reducing elongation, which is important for structural applications where stiffness and permanent set resistance are required.

Yield strength and UTS are also influenced by thickness; thinner gauges tend to exhibit higher work-hardening and slightly elevated strength after the same cold work compared with thicker plate due to processing differences. Hardness correlates with temper and serves as a practical field metric to assess degree of work-hardening and potential softening after thermal exposure. Fatigue performance is generally good for a non-heat-treatable aluminum alloy, especially when deformed in a manner that avoids stress concentrators and retains corrosion protection.

Property	O/Annealed	Key Temper (e.g., H32 / H116)	Notes
Tensile Strength (UTS)	200–260 MPa	320–360 MPa	UTS increases substantially with strain-hardening; exact values depend on gauge
Yield Strength (0.2% offset)	80–120 MPa	210–260 MPa	Yield is most sensitive to temper and cold-working history
Elongation	18–25%	6–14%	Ductility reduced in higher H tempers; fracture mode remains ductile
Hardness (HB)	40–55 HB	75–95 HB	Hardness rises with work-hardening and is used for QA checks

Physical Properties

Property	Value	Notes
Density	~2.66–2.70 g/cm³	Slightly lower than many steels, enabling weight savings
Melting Range	~570–645 °C	Solidus to liquidus range typical for wrought Al-Mg alloys
Thermal Conductivity	~120–150 W/m·K	Good thermal conduction; depends on alloying level and temper
Electrical Conductivity	~28–42 % IACS	Reduced from pure Al due to alloying; still suitable for conductive parts
Specific Heat	~0.90 J/g·K	Comparable to other aluminum alloys; important for heat capacity calculations
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Moderate thermal expansion; design allowances needed for thermal cycles

The relatively high thermal conductivity and moderate electrical conductivity make 535 a reasonable choice for thermal management components where corrosion resistance is required. Density combined with high specific strength leads to favourable strength-to-weight for structural parts. Thermal expansion should be considered in assemblies with dissimilar materials to avoid distortion or sealing issues during service temperature excursions.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Higher strength in cold-rolled gauges	O, H111, H32	Widely used for formed components and paneling
Plate	6–150 mm	Lower ductility in thick sections; heat input during fabrication matters	O, H116	Common in hulls and structural members
Extrusion	Wall thickness >1 mm	Strength varies with section and cooling	O, H111	Used for structural profiles and frames
Tube	0.5–10 mm wall	Straightening and forming affect final properties	O, H32	Pressure tubing and structural tubes for marine use
Bar/Rod	Ø 6–100 mm	Work-hardening limited in large sections	O, H112	Used for machined fittings and fasteners

Sheets and thin-gauge products are typically cold-rolled and can be aged or stabilized to improve stress-corrosion resistance, while plate production focuses on control of rolling and solution history to maintain toughness. Extrusions require careful die design to manage residual stresses and minimize distortions during straightening, and welding of plate or extruded structures usually calls for filler alloys matched to magnesium content.

Equivalent Grades

Standard	Grade	Region	Notes
AA	535	USA	Designation used in some supplier catalogs; falls within Al-Mg family
EN AW	~5xxx	Europe	Closely related to EN AW 5xxx series alloys; exact match depends on Mg content
JIS	A5xxx series	Japan	Equivalents exist in Japanese Al-Mg wrought alloy families
GB/T	Al-Mg series	China	Chinese standard grades approximate 5xxx-series compositions

Equivalent numeric designations across standards are approximate because exact element limits and impurity controls differ by specification. When substituting materials across standards engineers must check specific Mg, Mn and trace element limits as well as temper condition to ensure mechanical and corrosion performance equivalence.

Corrosion Resistance

Aluminum 535 exhibits robust general corrosion resistance in atmospheric and industrial environments due to the protective aluminum oxide film augmented by magnesium’s beneficial effect on passive film stability. In marine and chloride-bearing environments 535 performs well compared with many heat-treatable alloys, though localized pitting can occur where protective coatings are breached and crevice configurations are present.

Stress-corrosion cracking (SCC) susceptibility is low relative to high-strength 2xxx-series copper-bearing alloys and is controlled via low copper content and appropriate temper selection; however, heavily cold-worked tempers can show increased risk under tensile stress in aggressive environments. Galvanic interactions with more noble materials such as stainless steel can accelerate local corrosion on 535 unless electrical isolation or sacrificial protection is provided.

Compared with 6xxx and 7xxx families, 535 offers superior chloride resistance but lower achievable strength than peak-aged 6xxx/7xxx alloys. Designers often prefer 535 for marine structural components because it balances corrosion resistance with weldability and does not suffer the same post-weld temper-dependent softening seen in many heat-treatable alloys.

Fabrication Properties

Weldability

535 welds readily by common fusion processes such as TIG and MIG with low risk of hot cracking when appropriate filler metal and joint design are used. Weld fillers matched to Al-Mg compositions (for example, ER5356/5183 series) are recommended to preserve corrosion resistance and minimize intergranular phases. The heat-affected zone may experience some softening in highly worked tempers, so post-weld strain-relief or selecting stabilized tempers is often used for structural applications.

Machinability

As a non-heat-treatable Al-Mg alloy, 535 has fair machinability that is generally easier than many high-strength alloys but not as free-cutting as some Al-Si casting alloys. Carbide tooling and moderate cutting speeds with ample coolant provide the best balance of tool life and surface finish. Chip formation tends to be continuous and ductile; chip control and evacuation are key for high feed operations.

Formability

In the annealed O condition, 535 exhibits excellent formability and can sustain deep drawing, bending, and complex stamping operations with small bend radii relative to thickness. Cold working into H-tempers enhances strength but reduces formability; designers should specify O or H111 for parts requiring significant forming, and plan springback compensation when using H32/H116 tempers. Warm forming is seldom necessary but can be used to improve drawability for thick sections.

Heat Treatment Behavior

As a member of the 5xxx family, 535 is not responsive to classical solution-age heat treatments and does not have meaningful T6-type age hardening behavior. Strength adjustments are achieved primarily through controlled cold work and by selecting appropriate H tempers, sometimes combined with low-temperature stabilization to reduce sensitization.

Full annealing to the O condition is achieved by heating to the alloy-specific annealing range, typically between 300–415 °C followed by controlled cooling to restore ductility and soften the material. Designers often use strain-aging stabilization cycles or modest thermal exposure to relieve residual stresses while preserving corrosion resistance rather than to increase peak strength.

High-Temperature Performance

Strength retention of 535 degrades with increasing temperature; noticeable loss of yield and tensile properties occurs above approximately 100–150 °C under sustained loading. For intermittent exposure up to ~200 °C short durations may be acceptable, but prolonged service at elevated temperatures promotes recovery of cold-worked microstructures and a reduction in mechanical properties.

Oxidation at elevated temperatures is limited by the protective alumina layer, but sustained high-temperature exposure can lead to scaling and microstructural coarsening that degrade fatigue performance. Welded regions can be particularly sensitive to thermal cycles, so thermal management and post-heat treatment stabilization should be considered for assemblies exposed to elevated temperatures.

Applications

Industry	Example Component	Why 535 Is Used
Automotive	Structural panels and reinforcements	Good strength-to-weight and formability for stamped components
Marine	Hull panels, superstructure members	Excellent resistance to seawater corrosion and weldability
Aerospace	Secondary fittings and brackets	High corrosion resistance with competitive strength for non-critical parts
Electronics	Enclosures and heat-dissipating panels	Reasonable thermal conductivity and corrosion resistance

535 is commonly selected for applications that require durable corrosion performance combined with good manufacturability. Its ability to be welded, formed, and finished without complex thermal cycles makes it attractive for both marine and general structural uses where longevity and lifecycle costs are important.

Selection Insights

Choose 535 when you need a mid-strength, corrosion-resistant aluminum that can be readily welded and formed without heat treatment cycles. It is a practical choice for marine and transportation structures where chloride resistance and weld integrity are priorities.

Compared with commercially pure aluminum like 1100, 535 trades some electrical and thermal conductivity and slightly reduced formability for substantially higher strength and better structural performance. Against common work-hardened alloys such as 3003 or 5052, 535 typically offers higher strength with comparable or superior corrosion resistance, but it may be somewhat less formable than 3003 in certain tempers. Versus heat-treatable alloys such as 6061 or 6063, 535 is often preferred where post-weld properties and marine corrosion resistance matter more than achieving the maximum possible peak strength.

When deciding, weigh the need for welding and in-service corrosion resistance higher when selecting 535, and consider H-temper choices to balance forming and final strength. Cost and availability are generally favorable for 535, but confirm local supplier tempers and sheet/plate sizes to match fabrication processes.

Closing Summary

Aluminum alloy 535 remains a relevant engineering material by combining solid-solution magnesium strengthening with strong corrosion resistance and excellent weldability, offering a pragmatic alternative to both low-strength commercial alloys and heat-treatable high-strength grades. Its predictable work-hardening response and availability in a range of tempers make it a versatile choice for marine, transportation, and general fabrication applications where durability and manufacturability are key.