Aluminum 3105: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

3105 is a member of the 3xxx series of wrought aluminum alloys, primarily alloyed with manganese and modest amounts of magnesium. As a 3xxx-series alloy it is a non-heat-treatable, strain-hardenable material that gains strength predominantly through cold work rather than precipitation hardening.

Major alloying additions are manganese (Mn) and small controlled quantities of magnesium (Mg), with silicon, iron and trace elements present at low levels. These alloying elements raise strength relative to commercially pure aluminium while retaining good corrosion resistance and excellent formability.

The key traits of 3105 include moderate strength, good atmospheric corrosion resistance, high ductility in the annealed condition, and good general-purpose weldability. Typical industries and applications include architectural cladding and roofing, general sheet metal work, appliance panels, and some truck/trailer body panels where a balance of formability and corrosion resistance is required.

Engineers select 3105 when they need better mechanical performance than 1000-series alloys but do not require the higher-strength features or heat-treatable behavior of 6xxx or 2xxx series. It is often specified where forming operations dominate and where post-forming strength via work-hardening is acceptable and cost-effective.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (≥30%)	Excellent	Excellent	Fully annealed for maximum ductility and deep draw forming
H12	Low-Medium	Moderate (≈15–25%)	Very good	Excellent	Partial hardening by compressive or tensile strain, retains good formability
H14	Medium	Moderate (≈10–18%)	Good	Excellent	Common commercial temper for moderate strength and good formability
H16	Medium	Lower than H14 (≈8–15%)	Fair-Good	Excellent	Higher strain hardening for increased yield and tensile strengths
H18	Medium-High	Low-Moderate (≈6–12%)	Fair	Excellent	Heavier cold work for higher static strength
H24	Medium	Moderate (≈12–20%)	Good	Excellent	Solution treated + partial re-strain; improves stability for some forming processes

Temper significantly alters the trade-off between ductility and strength for 3105. Annealed O condition offers the greatest formability for complex stamping and deep drawing while H-tempers provide incremental strength increases through cold work and controlled strain hardening.

Selecting a temper is a manufacturing decision that depends on forming sequence, required final strength, and dimensional stability. For welded assemblies the annealed or lightly cold-worked tempers reduce risks of cracking and make distortion control easier.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.6	Silicon limited to minimize brittle intermetallics and maintain formability
Fe	≤ 0.7	Residual iron; controlled to limit coarse intermetallic particles that reduce ductility
Mn	0.7 – 1.3	Primary alloying element providing solid-solution strengthening and grain stabilization
Mg	0.2 – 0.7	Small Mg additions raise strength and improve strain-hardening response
Cu	≤ 0.25	Limited copper; small amounts improve strength but can reduce corrosion resistance
Zn	≤ 0.2	Kept low to avoid uncontrolled precipitates and to retain corrosion resistance
Cr	≤ 0.1	Trace levels; may be used to control grain structure in some mill batches
Ti	≤ 0.15	Deoxidizer / grain refiner in some processing streams
Others	Each ≤ 0.05, Total ≤ 0.15	Minor impurities / residuals; tightly specified for consistent properties

The chemistry of 3105 is tuned to deliver a balance of cold-work hardening and corrosion resistance. Manganese is the principal strengthening element providing grain-boundary strengthening without the need for heat treatment. Modest magnesium levels improve cold-work response and final strength after forming, while low copper and zinc limits preserve resistance to general corrosion and galvanic degradation.

Mechanical Properties

In tensile behavior 3105 follows typical 3xxx-series patterns: low yield strength in the annealed state with a continuous strain-hardening response when cold worked. Tensile strength and yield scale with temper and thickness; thin-gauge sheet will generally exhibit higher apparent strength due to work-hardening during rolling and coiling. Fatigue performance is acceptable for non-high-cycle critical components but is strongly influenced by surface finish and residual stresses from forming and welding.

Yield strength in O temper is low and ductility is high, making it ideal for forming; H14 and H16 temper levels offer moderate yield and tensile strengths while retaining reasonable elongation for moderate forming operations. Hardness correlates with cold work; H-temper material will exhibit higher Brinell or Vickers values than O-temper, and localized hardening in the heat-affected zone can occur with welding. Thickness effects are notable: heavier plate shows somewhat lower ductility and may have slightly lower strength per unit cross-section due to mill processing differences.

Property	O/Annealed	Key Temper (H14)	Notes
Tensile Strength	~90 – 140 MPa	~160 – 210 MPa	Wider ranges depend on gauge and mill processing; H-temper tensile increases ~40–80 MPa compared to O
Yield Strength	~25 – 60 MPa	~90 – 140 MPa	Yield rises rapidly with strain hardening; precise yield depends on percent cold work
Elongation	≥30% (thin gauges)	~10–18%	Elongation drops as temper increases; thicker gauges typically show reduced elongation
Hardness	HB 20–40	HB 40–70	Hardness increases with temper level and cold working; values are approximate and method-dependent

Physical Properties

Property	Value	Notes
Density	≈ 2.70 g/cm³	Typical for wrought Al-Mn alloys; important for strength-to-weight calculations
Melting Range	≈ 630 – 650 °C	Alloying depresses melting slightly below pure Al (660 °C); cast-related melting not applicable for wrought forms
Thermal Conductivity	≈ 130 – 170 W/m·K	Lower than pure Al but still good for heat dissipation tasks
Electrical Conductivity	≈ 30 – 45 % IACS	Reduced versus pure Al due to alloying; impacts EMI and conductor design
Specific Heat	≈ 900 J/kg·K	Approximate, useful for thermal mass and transient heating calculations
Thermal Expansion	≈ 23 – 24 µm/m·K	Similar to other Al alloys; relevant for thermal cycling and joining to dissimilar metals

3105 retains many of aluminum’s favorable physical traits: low density, good thermal conductivity, and a relatively high specific heat. These properties make it useful where weight reduction and moderate thermal transfer are needed, although its conductivity is appreciably lower than nearly-pure aluminum grades.

Designers should account for higher thermal expansion compared with steels and some other non-ferrous alloys, especially in assemblies with dissimilar materials where differential expansion can induce stresses or distortion during temperature excursions.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2 – 6.0 mm	Strength increases with H-tempers	O, H12, H14, H16	Most common form for architectural and appliance panels
Plate	>6.0 mm	Slightly reduced ductility vs sheet	O, H14, H18	Less common; used where thicker sections required
Extrusion	Complex cross-sections up to large profiles	Cold work after extrusion can raise strength	O then aged/cold-worked to H-status	Mn alloys are extrudable but 3xxx not as common as 6xxx for structural extrusions
Tube	Ø small to large, wall thickness variable	Dependent on fabrication (drawn or welded)	O, H14	Used for tubing where corrosion resistance and formability needed
Bar/Rod	Round/flat bars for light structural parts	Modest strength; increases with cold work	H14, H16	Less typical than sheet; used for formed components or fasteners in limited cases

Sheets and coils are the dominant commercial product forms for 3105, reflecting the alloy’s utility in cladding, roofing, and appliance panels. Plate and extrusion offerings exist but are less common and are selected where specific gauge or profile requirements outweigh the benefits of alternative alloys.

Processing differences between forms matter: rolled sheet receives substantial cold reduction and coiling which affects residual stresses and temper response. Extrusions and tubes will have their own as-extruded properties and may require post-processing (aging or cold work) to meet dimensional and strength specifications.

Equivalent Grades

Standard	Grade	Region	Notes
AA	3105	USA	UNS A93105; common North American designation
EN AW	3105	Europe	Often listed as EN AW-3105; chemistry and tolerances aligned with international wrought aluminium standards
JIS	A3105 (common form)	Japan	Local standards may list A3105 or equivalent Al-Mn-Mg composition
GB/T	3105	China	Chinese steel/aluminium standards typically use the same numeric designation for wrought aluminium series

The 3105 designation is broadly used in global standards and is generally consistent across regions in chemical makeup and application intent. Small discrepancies can arise from regional tolerance bands, permissible impurity levels, and mill certification practices. Buyers should request specific standard references and mill certificates to ensure compositional and mechanical conformity for critical projects.

Corrosion Resistance

3105 exhibits good resistance to general atmospheric corrosion and performs well in typical urban and rural environments. The controlled manganese and low copper content provide a balanced surface stability and reduce susceptibility to uniform corrosion; painted or coated finishes further enhance life for architectural use.

In marine environments, 3105 is serviceable for above-deck or sheltered applications but is not as robust as high-magnesium 5xxx-series alloys for immersed or splash-zone service. Chloride-induced pitting is more pronounced in seawater exposure than in alkaline atmospheres, so extra protection (coatings, anodizing, or sacrificial anodes) is recommended for prolonged marine exposure.

Stress corrosion cracking risk for 3105 is low under normal conditions since it is not precipitation-hardened; however, localized corrosion and hydrogen embrittlement in severely cathodic environments can still occur. When coupled galvanically to more noble metals like stainless steel or copper, 3105 will act as the anode and corrode preferentially unless electrically isolated or protected. Designers should plan jointing materials and coatings to control galvanic currents.

Compared with other alloy families, 3105 typically outperforms 1xxx series in strength at similar corrosion levels, while it lags behind selected 5xxx magnesium-rich alloys in aggressive marine or chloride-laden environments. Against 6xxx series alloys, 3105 offers better formability but lower structural strength and different anodizing appearance.

Fabrication Properties

Weldability

3105 welds readily by common fusion processes such as TIG (GTAW) and MIG (GMAW). Recommended filler wires include 4043 (Al-Si) for good flow and reduced hot cracking tendency, or 5356 (Al-Mg) when higher joint strength is required; the filler choice depends on base metal temper and required corrosion resistance. Hot-cracking risk in 3xxx alloys is low compared with some Al-Si cast alloys, but care must be taken with joint fit-up and heat input to minimize distortion and HAZ softening.

Machinability

Machinability of 3105 is moderate to poor compared with free-machining aluminium alloys and some 6xxx series grades. Typical machinability indices are lower than wrought 6xxx alloys; sharp carbide tools, high positive rake, and good chip evacuation are recommended. Cutting speeds should be adjusted down from 6xxx recommendations, and lubrication or air blast may be required for continuous chip control on thin-walled sections.

Formability

Formability in the annealed O temper is excellent, permitting deep drawing, stretch forming and complex bending operations. Minimum internal bend radii for O temper can often be as low as 0.5–1.0× thickness for simple bends, while H-tempers typically require 1–3× thickness to avoid cracking. Springback is moderate and predictable, and controlled pre-straining or intermediate anneals can be used to achieve complex shapes while maintaining dimensional control.

Heat Treatment Behavior

3105 is non-heat-treatable; strength is primarily developed through cold work (strain hardening). There is no practical solution treatment and aging path that produces significant precipitation hardening as with 6xxx or 2xxx alloys.

Annealing is used to restore ductility and relieve residual stresses. Typical industrial annealing ranges for 3xxx alloys are in the 300–415 °C range with a soak appropriate for section thickness; rapid quench is not required. T-tempers (artificial aging) are not applicable for producing meaningful additional strength in 3105, though some commercial practices combine solution anneal with mechanical re-strain to stabilize temper (e.g., H24-style processing).

High-Temperature Performance

Mechanical strength of 3105 degrades steadily with temperature; useful structural strength is substantially reduced above ~100–150 °C. Short-term exposures to elevated temperatures (for forming, brazing or welding) are tolerated, but sustained service at high temperature will reduce yield and tensile capacity. Oxidation of aluminum is self-limiting via a thin protective oxide film; however, at elevated temperatures oxidation rate and scale formation can increase and should be considered for long-term high-temperature use.

Weld heat-affected zones can show localized softening due to annealing effect of the weld thermal cycle, but absence of precipitation hardening means there is no reversion to much weaker states as seen in some heat-treatable alloys. For assemblies with significant high-temperature duty, engineers should evaluate creep and fatigue at service temperatures and consider higher-temperature alloys if required.

Applications

Industry	Example Component	Why 3105 Is Used
Automotive	Outer body panels, trim	Good formability for stamped panels; moderate strength after work-hardening
Marine	Sheltered structures, interior fittings	General corrosion resistance and ease of forming for architectural marine components
Aerospace	Non-structural fittings, fairings	Low density and formability for non-primary structural parts
Electronics	Thin housing panels, thermal shrouds	Balance of thermal conductivity and manufacturability for enclosures
Architecture	Cladding, roofing, gutters	Weather resistance, paintability, and long-term appearance stability

3105 is especially valuable where forming complexity, corrosion resistance and cost compete with requirements for moderate mechanical performance. Its combination of attributes means it remains a reliable choice for many sheet-metal dominated applications where higher-strength heat-treatable alloys are unnecessary.

Selection Insights

3105 is a practical choice when designers need more strength than commercially pure aluminium (e.g., 1100) while retaining excellent formability and corrosion resistance. Compared with 1100, 3105 trades a modest reduction in electrical and thermal conductivity for higher yield and tensile strength and improved mechanical stability during forming.

Against common work-hardened alloys like 3003 or 5052, 3105 typically sits between them in strength and corrosion resistance: it is stronger than 3003 in many tempers due to optimized Mn/Mg content but usually less corrosion-resistant in harsh chloride environments than magnesium-rich 5xxx alloys. Compared with heat-treatable materials such as 6061 or 6063, 3105 is selected when forming and final formability are prioritized and when lower cost and simpler fabrication (no solution/aging cycles) are advantageous despite lower peak strengths.

Choose 3105 when project drivers emphasize deep drawing or complex stamping, good atmospheric corrosion resistance, ease of welding and economical sheet availability. Avoid it when maximum structural strength, high-temperature stability, or superior marine immersion performance are mandatory; in those cases consider 6xxx or 5xxx series alloys respectively.

Closing Summary

3105 remains relevant as a versatile 3xxx-series aluminium that balances formability, weldability and corrosion resistance with moderate strength achievable through cold work. Its consistent performance in sheet and coil forms, broad availability, and ease of fabrication make it a practical specification for architectural, appliance, transport and general engineering applications where weight, manufacturability and lifecycle cost are key considerations.