Aluminum 3203: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

3203 is a member of the 3xxx series of aluminum alloys, a family defined by manganese as the principal alloying element. This series is classified as non-heat-treatable and gains strength primarily by solid-solution and strain (work) hardening rather than precipitation hardening.

Major alloying elements in 3203 are manganese with controlled additions of iron and trace elements such as copper, magnesium, chromium and titanium to tailor strength and formability. The strengthening mechanism is predominantly work-hardening combined with solid-solution strengthening from Mn and minor elements; conventional T-temper precipitation strengthening routes yield little additional strengthening for this alloy.

Key traits of 3203 include a balance of moderate strength, good corrosion resistance in many atmospheric and mildly corrosive environments, and very good formability in annealed conditions. Weldability is generally excellent for Al-Mn alloys, and 3203 is often selected for applications requiring deep draw, complex forming, or welded assemblies where a non-heat-treatable alloy is preferred.

Typical industries using 3203 are automotive sheet components, architectural panels, appliances and consumer goods, and certain marine and transportation subcomponents. Engineers choose 3203 over either purer commercial aluminum (for higher strength) or heat-treatable 6xxx/7xxx alloys (for better formability and weldability without relying on heat treatment), when a balance of cold-formability, weldability and resistance to corrosion is needed.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (≥25%)	Excellent	Excellent	Fully annealed; highest ductility for deep drawing
H14	Medium-High	Low–Moderate (6–12%)	Good	Good	Half-hard cold-worked; common for formed panels
H18	High	Low (3–7%)	Limited	Good	Full-hard cold-rolled; used where stiffness/strength needed
H24	Medium	Moderate (10–18%)	Good	Good	Strain-relieved condition; improved formability after limited work
T5 / T6 / T651	Not applicable	Not applicable	Not applicable	Not applicable	3203 is non-heat-treatable; T tempers do not produce precipitation strengthening

Temper has a first-order effect on mechanical performance for 3203 because the alloy is strengthened primarily by cold work. Moving from O to H-series increases yield and tensile strength substantially while reducing elongation and forming range.

In practice designers specify O for complex forming operations and draw-intensive parts, H14/H18 for finished products where dimensional stability and stiffness are required, and H24 when a compromise between formability and residual strength (after tempering) is desirable.

Chemical Composition

Element	% Range	Notes
Si	0.10–0.40	Controlled to minimize embrittling intermetallics; silicon improves castability in higher concentrations.
Fe	0.20–0.70	Typical impurity level; elevated Fe forms intermetallic particles that can affect surface finish and ductility.
Mn	0.6–1.5	Primary alloying element; contributes solid-solution strengthening and improved grain structure.
Mg	0.05–0.25	Minor strengthening contributor; too much Mg can reduce corrosion resistance.
Cu	0.05–0.25	Small additions increase strength but can reduce corrosion resistance and weldability if excessive.
Zn	≤0.25	Kept low to avoid embrittlement and to maintain formability and corrosion resistance.
Cr	0.03–0.20	Helps control grain structure and improves strength after thermomechanical processing.
Ti	≤0.10	Grain refiner during casting/solidification; assists in fine microstructure.
Others (each)	≤0.05	Includes trace elements such as V, Zr; remainder is aluminum (balance).

The manganese level is the primary lever for tuning strength in 3xxx alloys, while iron and silicon appear as residuals that affect particle formation and surface quality. Minor Cu and Mg provide incremental strength but must be controlled to preserve corrosion resistance and fabrication behavior.

Mechanical Properties

Tensile behavior in 3203 is strongly temper-dependent: in annealed (O) condition the alloy exhibits relatively low yield and tensile strength with high elongation and excellent necking resistance, while cold-worked tempers produce much higher yield strengths with reduced ductility. Yield and ultimate tensile strength scale with the degree of cold work and can vary significantly with gauge thickness due to through-thickness work-hardening gradients.

Hardness follows the tensile trend and is a useful proxy for estimating cold-work level during fabrication. Fatigue performance is influenced by surface finish, tensile mean stress and the presence of intermetallic particles; properly prepared surfaces and conservative design detail can yield robust fatigue life comparable to other 3xxx-series alloys.

Thickness and processing history are important: thinner gauges cold-roll to higher strengths and lower ductility more readily, whereas thicker sections can retain more ductility after the same amount of cold work. Welded assemblies can show localized softening in heat-affected zones for cold-worked tempers, which must be considered in structural designs.

Property	O/Annealed	Key Temper (H14)	Notes
Tensile Strength	110–140 MPa	180–240 MPa	Typical ranges; final values depend on thickness and degree of cold work.
Yield Strength	35–60 MPa	120–190 MPa	Yield increases markedly with cold working; H14 commonly specified for formed parts.
Elongation	25–35%	6–12%	Ductility drops substantially with higher tempers; O is used for deep drawing.
Hardness (HB)	30–45 HB	60–95 HB	Hardness correlates to temper and gives quick feedback during QC.

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for aluminum–manganese alloys; useful for mass calculations.
Melting Range	~600–650 °C	Solidus/liquidus vary slightly with composition; narrow range relative to casting alloys.
Thermal Conductivity	120–160 W/m·K (25 °C)	Slightly below pure Al due to alloying; good for thermal management.
Electrical Conductivity	~30–45 % IACS	Reduced compared with pure aluminum; conductivity decreases with cold work.
Specific Heat	~0.90 J/g·K (900 J/kg·K)	Typical aluminum specific heat used in thermal calculations.
Thermal Expansion	~23–24 µm/m·K (20–100 °C)	Coefficient of thermal expansion similar to other Al alloys; relevant for joining to dissimilar metals.

The combination of relatively high thermal and electrical conductivity with low density makes 3203 attractive for weight-sensitive thermal applications where extreme conductivity is not required. Thermal expansion and conductivity figures should be used when designing assemblies with dissimilar materials to avoid joint stress or thermal mismatch.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–4.0 mm	Cold-roll work-hardens; thinner gauges reach higher tempers	O, H14, H24	Widely used for panels and formed parts; deep draw in O condition.
Plate	4–25+ mm	Limited cold workability in very thick sections	O, H24	Used for structural components where thickness needed; formability decreases with thickness.
Extrusion	Sections up to 1000 mm	Mechanical properties depend on extrusion ratio and subsequent cold work	O, H12/H14	Extruded profiles for architectural framing and channels.
Tube	0.5–6.0 mm wall	Strength depends on forming (seam-welded vs seamless)	O, H14	Common in HVAC and low-pressure fluid systems.
Bar/Rod	3–50 mm	Solid rods retain annealed properties unless cold drawn	O, H18	Used for machined components, fasteners and forming stock.

Processing differences drive application decisions: sheet is the most common and benefits from coil processing, plate and extrusions require longer thermal cycles and reduced cold work. Welded assemblies often start from O or H24 stock, then may be cold worked for final dimensional tolerances.

Equivalent Grades

Standard	Grade	Region	Notes
AA	3203	USA	Designation for this alloy in the Aluminum Association system.
EN AW	— (closest EN AW-3003 / EN AW-3105)	Europe	No exact EN equivalent; 3003/3105 are the nearest commercial counterparts in composition and behavior.
JIS	A3003 (approx.)	Japan	Japanese standards do not typically list 3203 specifically; A3003 is compositionally similar.
GB/T	3xxx-series (closest 3003)	China	Chinese designations mirror the general chemistry of 3xxx alloys; direct 3203 equivalents are uncommon.

Subtle differences across standards arise from allowable impurity limits and specific trace additions such as Cr or Ti which affect grain structure and forming. When substituting, engineers must compare exact certified chemical ranges, mechanical property tables, and tempers; a direct one-to-one replacement is not always acceptable for critical applications.

Corrosion Resistance

3203 exhibits good general atmospheric corrosion resistance characteristic of Al-Mn alloys, forming a stable and adherent oxide film that protects the substrate in many urban and industrial environments. The alloy tolerates periodic wet/dry cycles well and commonly used finishes such as anodizing improve both appearance and corrosion protection.

In marine or highly chloride-bearing atmospheres, 3203 performs adequately for many structural and non-structural applications but is not as corrosion-resistant as high-magnesium 5xxx series alloys in severe saltwater immersion. Localized pitting can occur on exposed surfaces if protective coatings or anodic treatments are not applied, and welds should be protected to avoid crevice corrosion at joints.

Stress corrosion cracking (SCC) susceptibility is low relative to certain high-strength heat-treatable alloys, but designers should still minimize tensile residual stresses and sharp stress concentrators in components exposed to aggressive environments. Galvanic interactions follow standard aluminum rules: avoid direct contact with noble metals without insulation; use sacrificial anodes or isolating materials when mated with steel or copper to prevent accelerated corrosion.

Fabrication Properties

Weldability

3203 welds readily with conventional fusion processes including TIG (GTAW) and MIG (GMAW), producing ductile weld metal and good fusion when proper cleaning and joint fit-up are observed. Typical filler alloys include 4043 (Al-Si) and 5356 (Al-Mg) depending on required ductility and corrosion resistance, with 4043 often chosen to minimize hot-cracking risk. Hot-cracking is low in Al-Mn alloys, but attention to joint design, heat input and post-weld distortion control is essential; cold-worked tempers will show HAZ softening requiring consideration in structural designs.

Machinability

Machinability for 3203 is moderate and typically poorer than high-silicon free-cutting aluminum alloys; the alloy machines well with carbide tooling and rigid setups. Recommended approaches include higher cutting speeds than steels but lower than for free-cutting aluminums, heavy use of positive rake inserts, and abundant coolant or air blast to avoid built-up edge and long stringy chips. Surface finish and dimensional control are generally excellent when chips are controlled and tool wear is managed.

Formability

Formability is excellent in the O temper where the alloy supports deep drawing, stretch forming and complex bending operations with minimal cracking. For bend work, recommended minimum inside bend radii are approximately 1–2× thickness in O condition and 3–4× thickness in H14/H18 tempers to avoid cracking. Springback is moderate and must be compensated for in tooling design; some designs use intermediate anneals to restore ductility after heavy cold work.

Heat Treatment Behavior

As a non-heat-treatable alloy, 3203 does not respond to solution heat treatment and aging in the way that 6xxx or 7xxx alloys do; artificial aging yields negligible precipitation hardening. Attempts to age the alloy at typical T-temper temperatures will not produce the same step-change in strength seen in heat-treatable families.

Annealing (recrystallization) and controlled anneal cycles are the primary thermal treatments used with 3203 to restore ductility after cold work. Typical full-anneal temperatures are in the 350–415 °C range with controlled cooling to attain an O temper; partial anneals and stress-relief cycles are used to reach H24 or strain-relieved conditions without fully softening the material.

High-Temperature Performance

3203 exhibits progressive strength loss with increasing temperature; long-term continuous service above about 100–150 °C will show measurable declines in yield and tensile strength. Short-term elevated-temperature exposure up to approximately 200 °C may be tolerated for intermittent service, but designers must account for reduced modulus, creep effects and potential microstructural recovery in cold-worked tempers.

Oxidation resistance is typical of aluminum alloys: a thin oxide layer forms quickly and retards further oxidation but surface scaling is not an issue at the temperatures relevant to most 3203 applications. Weld HAZs and cold-worked regions are the most temperature-sensitive zones and can experience softening or diminished mechanical capability when