Aluminum 4N01: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

4N01 is catalogued in the 4xxx family of aluminum alloys, a group principally characterized by silicon as a controlled additive and by alloys designed for good weldability and thermal stability. In industrial practice 4N01 is used as a wrought alloy with compositional tailoring that places it between classic 3xxx (Al–Mn) and 4xxx (Al–Si) behavior, which yields a balance of formability, moderate strength, and reliable fabrication performance.

Major alloying elements in 4N01 include silicon and manganese as intentional additions, with residual iron and trace elements such as titanium and chromium used for grain control and microstructure stabilization. Its strengthening derives primarily from solid-solution effects and work-hardening during fabrication rather than from precipitation hardening, so it is classed functionally as a non-heat-treatable, strain-hardenable alloy.

Key traits of 4N01 include moderate tensile strength, good general corrosion resistance in atmospheric environments, superior weldability compared with many heat-treatable alloys, and very good cold formability in annealed tempers. Typical industries using 4N01 include transportation (body panels and non-structural components), building envelopes, light appliances, and certain extrusion and tubing markets where a combination of formability and corrosion resistance is required.

Designers choose 4N01 over other alloys when a component requires good manufacturability (deep drawing, hemming, welding) with modest strength and weight savings, and where the priority is stable performance in welded assemblies rather than achieving the highest possible strength. The alloy is often selected when cost, availability, and predictable HAZ behavior during welding are important selection drivers.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High	Excellent	Excellent	Fully annealed; best for deep drawing and forming
H12	Low–Moderate	Moderate	Very Good	Excellent	Partial hardening by rolling; retains good ductility
H14	Moderate	Moderate–Low	Good	Excellent	Common commercial temper for stiffened sheet parts
H24	Moderate–High	Moderate	Good	Excellent	Work-hardened and stabilized for improved strength
H32	Moderate	Moderate	Good	Excellent	Strain-hardened plus stabilized; resistance to softening
T4 (limited)	Moderate	Moderate	Good	Excellent	Natural aging after solutionizing; limited utility since alloy is mainly non-heat-treatable

Temper significantly alters the trade-off between strength and ductility for 4N01 since the alloy relies on strain hardening rather than precipitation strengthening. Annealed (O) conditions deliver maximum forming capability and drawability, while H-series tempers produced by controlled cold work and stabilization increase yield and tensile strength at the expense of elongation and tight bendability.

Chemical Composition

Element	% Range	Notes
Si	0.4–1.0	Silicon improves fluidity during casting and increases weldability; moderate levels reduce melting range and help HAZ stability.
Fe	0.3–0.8	Iron is a common impurity that forms intermetallics; elevated Fe lowers ductility and increases brittle particle population.
Mn	0.6–1.2	Manganese provides solid-solution strengthening and improves resistance to recrystallization and corrosion.
Mg	0.02–0.20	Magnesium is kept low to avoid promoting age-hardening; trace Mg influences strength and work-hardening rate.
Cu	0.02–0.20	Copper typically remains low; higher Cu improves strength but can decrease corrosion resistance and weldability.
Zn	0.02–0.20	Zinc is limited; higher Zn raises strength slightly but can reduce corrosion resistance in marine environments.
Cr	0.02–0.15	Chromium is used in small amounts for grain refinement and to suppress grain boundary precipitates.
Ti	0.01–0.10	Titanium is a deoxidizer and grain refiner; small additions improve forgeability and control inclusions.
Others	≤0.15 (each)	Trace elements such as Zr, Ni, and Pb are typically minimized; total impurities limited to preserve properties.

The chemistry of 4N01 is tuned to favor cold formability and weldability while delivering moderate strength through Mn and Si contributions. Silicon lowers the melting interval and helps in welding and brazing contexts, whereas manganese stabilizes the microstructure against annealing and provides incremental strength without invoking heat-treatment cycles.

Mechanical Properties

The tensile behavior of 4N01 exhibits a pronounced dependence on temper and thickness, with annealed material showing low yield and high elongation while H-tempers show increased yield and reduced ductility. Tensile strength values are moderate compared with heat-treatable alloys; designers should account for reduction in ductility and increased springback as cold work increases.

Yield strength is typically low in O condition and increases predictably with H-series cold work; the alloy shows linear work-hardening response up to moderate strain levels and then strain-age stabilization. Fatigue performance is adequate for non-critical cyclic loads, but surface finish, residual stresses from forming and welding, and thickness play strong roles in endurance limit behavior.

Hardness in 4N01 is relatively low in annealed material and increases with temper and cold work; hardness correlates with yield and tensile increases and can be used as a quick shop-floor indicator of temper. Thickness effects are significant: thinner gauges tend to achieve higher effective strength in rolling and forming operations and show better quench homogeneity during processes that involve rapid cooling.

Property	O/Annealed	Key Temper (e.g., H14/H24)	Notes
Tensile Strength	80–120 MPa	150–220 MPa	Values depend on gauge and degree of cold work; H24 shows notable gains vs O.
Yield Strength	30–60 MPa	90–170 MPa	Yield increases markedly with strain hardening; for design use the lower bound for thick sections.
Elongation	25–40%	8–20%	Annealed material is highly ductile; elongation decreases as temper rises.
Hardness	20–40 HB	40–75 HB	Hardness increases with H-temper; used as QA metric for temper verification.

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Standard aluminum density; useful for mass and stiffness calculations.
Melting Range	~600–660 °C	Alloying widens the melting interval relative to pure Al; silicon narrows the solidification range.
Thermal Conductivity	120–150 W/m·K	Relatively high thermal conductivity; slightly below pure Al due to alloying.
Electrical Conductivity	~30–45 % IACS	Alloying reduces conductivity relative to pure aluminum but remains acceptable for many electrical applications.
Specific Heat	~0.90 J/g·K	Useful for thermal transient calculations in heat-sinking applications.
Thermal Expansion	23–24 ×10⁻⁶ /K (20–100 °C)	Typical aluminum thermal expansion; important for differential expansion design with steels and composites.

The physical properties make 4N01 suitable for applications where thermal transport and low density are priorities but where absolute electrical conductivity is not the dominant criterion. Thermal expansion and conductivity figures must be considered in assemblies that include dissimilar materials to avoid thermal stress and galvanic consequences.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6 mm	Uniform; higher effective strength in thinner gauges	O, H12, H14, H24	Widely used for bodywork, panels, and facades.
Plate	6–25 mm	Slightly lower work-hardening per pass; greater through-thickness constraints	O, H32	Used for structural covers and thicker fabricated parts.
Extrusion	Wall thickness 1–20 mm	Strength depends on solution treatment and stretch	O, H14, H24	Good for complex profiles where weldability and extrusion surface quality matter.
Tube	Ø 6–300 mm	Circumferential properties influenced by processing; welded and seamless options	O, H14	Used for hydraulic housings, architectural tubes, and light structural members.
Bar/Rod	Ø 3–80 mm	Cold-drawn bars show improved strength by work-hardening	H12, H14	Used for machined components and fittings where fabrication stability is needed.

Processing route strongly influences final mechanical behavior: sheet rolling imparts preferred textures that affect formability and stiffness, while extrusions benefit from frictional heat and controlled quench to achieve consistent microstructure. Fabrication choices — whether to use welded tubes or extruded profiles — depend on dimensional tolerances, surface quality, and post-forming operations such as painting or anodizing.

Equivalent Grades

Standard	Grade	Region	Notes
AA	4N01	USA	Commercial designation used for local procurement and spec sheets.
EN AW	4xxx (approx.)	Europe	Comparable alloys exist within the EN AW 4xxx family; direct cross-reference requires exact chemistry.
JIS	A4xxx (approx.)	Japan	Japanese standards include similar Si/Mn alloys; equivalence needs verification by composition.
GB/T	4N01	China	Chinese GB/T designation commonly used in regional supply chains with matched chemistry and tempers.

Regional standards and numbering systems are not always one-to-one; small differences in impurity limits, maximum copper, or manganese can cause meaningful differences in corrosion and mechanical performance. When replacing or specifying equivalent grades, engineers must compare full chemical and mechanical specifications, temper definitions, and supplier heat treatment records rather than relying on nomenclature alone.

Corrosion Resistance

4N01 generally exhibits good resistance to atmospheric corrosion due to the passive aluminum oxide layer and the stabilizing effect of manganese against intergranular attack. In rural and urban atmospheres the alloy performs comparably to other non-heat-treatable aluminum grades and typically outperforms low-alloy steels in terms of maintenance-free life.

In marine environments 4N01 offers moderate performance; it is more resistant to general corrosion than many copper-bearing alloys but is susceptible to localized pitting in chloride-rich conditions if not properly surface treated. Protective finishes such as anodizing, conversion coatings, or suitable paint systems are commonly specified to extend service life in offshore or coastal applications.

Stress corrosion cracking susceptibility is low for 4N01 compared with high-strength heat-treatable alloys, because it lacks the precipitate structures that promote SCC. However, galvanic interactions with more noble metals (e.g., copper, stainless steels in passive condition) require design attention: aluminum will be anodic and can corrode preferentially unless electrically isolated or protected by appropriate coatings.

Compared with other alloy families, 4N01 offers better corrosion resistance than many Cu-containing alloys and comparable behavior to 3xxx and 5xxx families in non-marine settings. Against 6xxx and 7xxx series, 4N01 is generally more tolerant of marine exposure but does not reach the peak strength of those heat-treatable alloys.

Fabrication Properties

Weldability

4N01 demonstrates excellent weldability with common fusion welding processes such as MIG (GMAW) and TIG (GTAW); the alloy has a relatively broad melting interval and produces minimal hot-cracking when best practices are followed. Recommended filler alloys are those matched for ductility and corrosion resistance — ER4043 is a common Si-rich filler for welded assemblies, and ER5356 can be used where higher weld strength is desirable, though weld metal composition will influence corrosion and mechanical balance. HAZ softening is limited compared with precipitation-hardenable alloys, and post-weld mechanical property changes are predictable and manageable with appropriate joint design and thermal input control.

Machinability

As a relatively ductile, strain-hardenable aluminum alloy, 4N01 has fair machinability typical of wrought aluminum; it machines better in H-temper where strength and rigidity reduce chatter. Carbide tooling with TiAlN or TiN coatings is recommended for higher speed cutting, with moderate feed rates and higher spindle speeds to produce short, controlled chips. Coolant and chip evacuation strategies are important to avoid built-up edge and tool clogging, and pre-hardening or temper selection can significantly affect tool life and finish.

Formability

Formability is excellent in the fully annealed (O) condition, enabling deep drawing, stretching, hemming, and complex multi-step stamping operations without cracking. Typical minimum inside bend radii in O temper can be on the order of 1–2× material thickness for simple bends and 2–4× thickness for more severe forming, while H-temper parts require larger radii and may need pre-heating or intermediate anneals. The alloy responds predictably to cold working; designers frequently specify an anneal after heavy forming to relieve springback and restore ductility before finishing operations.

Heat Treatment Behavior

4N01 is functionally non-heat-treatable; it does not acquire significant precipitation strengthening from artificial aging cycles used in 6xxx or 7xxx alloys. Attempts to apply standard solution-treatment and artificial aging produce limited additional strength because the alloy lacks the Mg–Si or Zn–Mg systems that form strengthening precipitates.

Strength manipulation is therefore performed through controlled cold work (work hardening) and by thermal stabilization (low-temperature anneals) to set a desired combination of strength and elongation. Full annealing (O) restores maximum ductility, while partial anneals and stabilization treatments (T temper designations where applicable) are used to relieve residual stresses and moderate the effects of prior cold reduction.

High-Temperature Performance

Mechanical strength in 4N01 declines progressively with temperature and designers typically limit continuous operating temperatures to below ~150 °C to avoid significant reductions in yield and fatigue performance. Short-term exposure to higher temperatures (up to ~250 °C) can be tolerated but will cause measurable softening and potential microstructural recovery that reduces work-hardened strength.

Oxidation is minimal at temperatures relevant for most service conditions because aluminum forms a protective oxide film, but prolonged high-temperature exposure can thicken oxide layers and alter surface finish and paint adhesion. HAZ behavior during welding at elevated local temperatures is benign relative to heat-treatable alloys, but designers should account for temporary loss of strength and possible distortion adjacent to welds.

Applications

Industry	Example Component	Why 4N01 Is Used
Automotive	Outer body panels, inner reinforcement panels	Excellent formability for stamping, good weldability, and corrosion resistance at reasonable cost
Marine	Non-structural decking, fittings	Balanced corrosion resistance and fabricability for coastal and light marine use
Aerospace	Secondary fittings, fairings	Good strength-to-weight for non-primary structural components and good joinability
Electronics	Heat spreader plates, housings	High thermal conductivity with light weight and reliable fabrication
Building & Architecture	Cladding, soffits, window frames	Formability, aesthetic surface finishing, and weathering performance

4N01 is typically deployed where a combination of formability, weldability, and adequate strength is required without the need for complex heat-treatment cycles. Its role is often complementary to higher-strength alloys where cost-effective manufacturability and corrosion performance drive material choice.

Selection Insights

When selecting 4N01, choose it for applications that prioritize formability, weldability, and corrosion tolerance over maximum achievable strength. Its non-heat-treatable nature simplifies fabrication, reduces risk of HAZ embrittlement, and lowers processing cost relative to precipitation-hardenable alloys.

Compared with commercially pure aluminum (1100), 4N01 offers noticeably higher strength with a modest trade-off in electrical conductivity and slightly reduced formability, making it preferable for load-bearing sheet applications. Against work-hardened alloys such as 3003 or 5052, 4N01 sits similarly or slightly higher in strength while offering comparable corrosion resistance and improved weldability in some joint configurations.

Compared with heat-treatable alloys like 6061 or 6063, 4N01 provides easier weldability and better predictability in HAZ performance at the cost of lower peak strength; select 4N01 when simplified processing, superior forming, or cost-driven production outweighs the need for maximum strength or stiffness.

Closing Summary

4N01 remains a pragmatic engineering choice where a balance of formability, corrosion resistance, and dependable weldability is needed without the complexity of heat treatment, and it continues to serve diverse industries where predictable fabrication and life-cycle performance are prioritized over maximum strength.