Aluminum A365: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A365 is conventionally classified within the lower-strength wrought aluminum families and is most commonly grouped with the 3xxx-series manganese-bearing alloys for practical engineering discussions. Its principal alloying addition is manganese, with small controlled amounts of silicon, iron, copper, magnesium and trace elements used to tune strength, formability and corrosion resistance. Strengthening for A365 is principally by strain hardening (work-hardening) and microstructural control during thermo-mechanical processing rather than by classical precipitation hardening; it is therefore considered non-heat-treatable for significant increases in strength. Typical traits include moderate tensile and yield strength, very good formability in softened conditions, acceptable atmospheric corrosion resistance, and good weldability; these attributes make it a choice for formed non-structural and semi-structural components where ductility and corrosion resistance are prioritized.

A365 finds application across industries that require good formability and corrosion performance at modest cost, including architectural panels, lightweight housings, HVAC components, and certain automotive trim and secondary structural parts. The alloy is selected when design drivers favor forming, ductility and surface finish over maximum specific strength, or when fabrication routes involve extensive bending and drawing operations. Its machinability is moderate and its thermal and electrical conductivities remain relatively high compared with higher-alloyed, heat-treated Al grades. Engineers choose A365 over higher-strength heat-treatable alloys when post-forming heat treatments are impractical or when service environments demand the better general corrosion behavior of manganese-alloyed aluminum.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–35%)	Excellent	Excellent	Fully annealed condition for maximum ductility and formability
H14	Medium	Low–Moderate (6–12%)	Good	Very good	Strain-hardened to a quarter hard; common for formed sections
H16	Medium-High	Moderate (8–14%)	Good	Very good	Half-hard; more strength with reduced drawability
H18	High	Low (4–10%)	Fair	Good	Full-hard condition for higher stiffness in formed parts
T4 / T5 / T6 / T651	Not applicable / Limited	N/A	N/A	N/A	These classical heat-treated tempers are generally not applicable; A365 is non-heat-treatable for precipitation strengthening
H22 / H24 etc	Variable	Variable	Variable	Good	Multiple-step strain hardening and partial anneals to tailor strength–ductility balance

Temper has a primary and practical impact on A365 performance: annealed (O) offers the maximum forming window while H‑tempers trade ductility for strength via controlled cold work. Because the alloy does not respond to precipitation hardening like 6xxx alloys, designers rely on mechanical tempering (H‑series) and controlled annealing cycles to achieve required mechanical targets.

Chemical Composition

Element	% Range	Notes
Si	0.10–0.60	Controlled to limit brittle intermetallics and retain formability
Fe	0.20–0.70	Common impurity; excessive Fe reduces ductility and surface finish
Mn	1.00–1.80	Primary alloying element for strengthening and grain structure control
Mg	0.05–0.50	Low levels may appear; contributes modest solid-solution strengthening
Cu	0.02–0.20	Kept low to preserve corrosion resistance; increases strength if present
Zn	≤0.10	Kept minimal to avoid embrittlement and galvanic concerns
Cr	0.02–0.25	Small amounts improve recrystallization control and HAZ stability
Ti	0.02–0.15	Grain refiner in cast/wrought processing; trace levels help microstructure
Others	Balance Al, +trace (≤0.15 each)	Includes Zr or rare additions; residuals limited by spec

The composition of A365 is tuned to balance work-hardening response, corrosion resistance and formability. Manganese is the intentional strengthener that refines grain size and provides modest solid-solution and dispersion strengthening; iron and silicon are controlled to avoid coarse intermetallic phases that embrittle during forming. Trace elements such as chromium and titanium act as recrystallization inhibitors and grain refiners, which are important for maintaining consistent mechanical properties after thermomechanical processing.

Mechanical Properties

A365 exhibits tensile behavior characteristic of non-heat-treatable Mn-bearing alloys: in the annealed condition it displays relatively low tensile and yield strength but high elongation and excellent energy absorption in forming operations. Cold working raises yield and tensile strength proportionally while reducing uniform and total elongation; work-hardening curves are relatively linear up to moderate strain levels and the alloy shows good strain-age stability at ambient temperatures. Hardness tracks temper and cold work: O-temper yields low Brinell/Vickers numbers beneficial for forming, while H‑tempers can double hardness for improved wear or stiffness.

Fatigue performance of A365 is moderate and largely dominated by surface condition, finish, and the presence of inclusions or Fe-rich intermetallics; shot-peening and surface treatments can significantly improve fatigue life. Thickness effects are typical of aluminum alloys: thinner gauges cold work and respond more readily to strain hardening, while thicker sections retain ductility but may contain larger microstructural heterogeneities that reduce fatigue and formability. Heat-affected zones from welding can locally reduce strength due to recovery and recrystallization, but overall toughness and ductility remain acceptable for many fabricated structures.

Property	O/Annealed	Key Temper (e.g., H14)	Notes
Tensile Strength	~110–140 MPa	~200–260 MPa	Values depend on cold work level and thickness; reported ranges are typical for wrought Mn-alloyed grades
Yield Strength	~45–80 MPa	~160–220 MPa	Yield rises rapidly with strain hardening; onset of yield plateau is temperature and processing dependent
Elongation	~20–35%	~6–12%	Ductility falls with increased hardness; elongation measured on standard gauge per ASTM/EU norms
Hardness	~30–45 HB	~65–95 HB	Hardness correlates with temper and cold work; surface treatments alter readings

Physical Properties

Property	Value	Notes
Density	2.70 g/cm³	Typical for aluminum alloys; beneficial for high specific stiffness designs
Melting Range	~605–655 °C	Alloying slightly depresses melting point relative to pure Al; solidus–liquidus range depends on local composition
Thermal Conductivity	~120–150 W/m·K	High relative to steels; reduced slightly from pure aluminum by alloying additions
Electrical Conductivity	~25–35 % IACS	Lower than pure Al and commercial-purity grades due to alloying; adequate for many electrical applications
Specific Heat	~0.88–0.92 J/g·K	Typical for aluminum alloys near room temperature
Thermal Expansion	~23–24 ×10⁻⁶ /K	Similar to other Al alloys; important to consider in assemblies with dissimilar materials

The physical property set places A365 in the class of lightweight, thermally conductive materials suitable for heat dissipation applications, where electrical conductivity and thermal conductivity remain useful but are traded off for mechanical performance. Thermal expansion is significant compared with steels and must be accommodated in mixed-metal assemblies to avoid thermal stress or joint fatigue. Density and specific heat make the alloy advantageous where mass-sensitive thermal management is required.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Homogeneous through thickness; cold workable	O, H14, H16	Common for architectural and fabricated panels; excellent surface finish
Plate	6–25 mm	Bulk sections require controlled rolling for consistent properties	O, H18	Thicker gauges may show slightly lower ductility and require heavier forming forces
Extrusion	Profiles from 5–80 mm cross-section	Strength varies with extrusion ratio and subsequent cold-work	O, H1x	Extruded sections can be aged for dimensional stability but not precipitation-strengthened
Tube	0.5–10 mm wall	Seamless/welded tubes maintain decent mechanicals after forming	O, H14	Used in HVAC and structural tubing; bendability dependent on temper
Bar/Rod	Ø3–50 mm	Cold drawing increases strength and reduces elongation	H12–H18	Common for fasteners, machined fittings and structural pins

Form factor dictates processing windows: thin sheet can be drawn and spun easily in the annealed condition while plate and bar require heavier forming methods or staged annealing. Extrusion profiles benefit from tight control of billet composition and homogenization to avoid surface cracking and to obtain consistent mechanical properties, especially when post-extrusion drawing or bending is required. Welded forms such as tubes and fabricated assemblies should consider HAZ softening and design weld sequences to minimize distortion.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A365	USA	Aluminum Association designation for the alloy covered in this document
EN AW	No exact equivalent	Europe	Closest practical EN grades are AW-3003 / AW-3004 for similar Mn-content; composition and property differences exist
JIS	Closest: A3003 family	Japan	JIS has 3000-series equivalents; direct one-to-one match is not always available
GB/T	Closest: 3××× series	China	Chinese standards provide 3xxx-series alloys with similar Mn ranges; check supplier spec for exact mapping

There is frequently no single global direct equivalent for A365 because regional standards specify slightly different limits and impurity allowances; therefore, conversions are approximate. When substituting materials across regions or suppliers, engineers must compare detailed chemistry, mechanical property guarantees and processing histories (e.g., mill anneal vs. laboratory anneal) rather than relying solely on nominal grade names.

Corrosion Resistance

A365 provides good general atmospheric corrosion resistance due to its low copper content and moderate manganese alloying, which promotes a protective oxide film in many environments. In industrial and urban atmospheres the alloy performs well when left uncoated, but localized corrosion may occur in chloride-rich environments if the surface is damaged or if iron-rich intermetallics are present. Marine exposure requires careful design and protective finishes; while A365 resists uniform corrosion, pitting and crevice corrosion are possibilities on unprotected surfaces, especially in stagnant salt-laden conditions.

Stress corrosion cracking susceptibility for A365 is relatively low compared with higher-strength heat-treated alloys, because the alloy does not achieve the high yield strengths that promote SCC in aluminum–copper or high-strength 7xxx series alloys. Galvanic interactions follow typical aluminum behavior: A365 is anodic to most stainless steels, copper, and high-copper alloys, so insulating layers or sacrificial design considerations are necessary when joining dissimilar metals. Compared with 5xxx magnesium-bearing alloys, A365 generally exhibits similar or slightly better localized corrosion resistance, while 6xxx series alloys may show better anodic behavior when properly anodized or coated.

Fabrication Properties

Weldability

Welding of A365 is straightforward with conventional fusion processes such as TIG and MIG when filler alloys are properly chosen; filler metals with similar composition to 3xxx-series alloys or low-strength Al‑Mn fillers minimize hot-cracking risk. Because A365 is not precipitation-hardenable, post-weld strength recovery is not an issue, but localized softening and grain growth in the HAZ can reduce load-bearing capacity when compared to the cold-worked parent metal. Preheat and interpass temperature control are generally unnecessary for thin sections, but attention to cleanliness, oxide removal and proper shielding gas is critical to prevent porosity and poor fusion.

Machinability

Machinability of A365 is moderate and comparable to other non-heat-treatable aluminum alloys; it machines well at high spindle speeds with appropriate lubricants and sharp carbide tooling. Tools should be selected for good thermal resistance and edge geometry that promotes short, broken chips; chip control can be helped by using chip breakers and by optimizing feed rates. Surface finish achievable by turning and milling is good, but tool vibration and workpiece clamping must be controlled to avoid chatter, especially in softer annealed tempers.

Formability

Formability is one of the strongest attributes of A365, particularly in the O temper where deep drawing, bending and stretch-forming can be performed with relatively tight radii. Recommended minimum bend radii depend on gauge and temper, but an annealed sheet can often be formed to radii as low as 1–2× thickness depending on geometry and lubrication; H‑tempers require larger radii to avoid edge cracking. Cold-working response is predictable, enabling designers to plan staged forming with intermediate anneals to recover ductility and minimize springback.

Heat Treatment Behavior

Because A365 is effectively non-heat-treatable for precipitation strengthening, thermal processing is used primarily for annealing and for controlling recrystallization and grain size. Annealing cycles are typically performed at temperatures that allow recovery and recrystallization without incipient melting, restoring ductility for subsequent forming operations; a common industrial anneal for similar Mn alloys is in the 300–420 °C range depending on section thickness and desired grain size. Stabilization and recrystallization control can be achieved via small alloying additions (Cr, Ti) that pin grain boundaries; these elements alter the temperature/time window for annealing.

Work hardening is the main strengthening pathway: room-temperature cold work increases dislocation density and raises yield and tensile strength predictably, and controlled partial anneals can be used to achieve intermediate tempers (H22, H24, etc.). T‑tempers used for heat-treatable Al alloys (T6, T5, etc.) do not provide the same strengthening mechanisms in A365 and are therefore not effective for producing high precipitation-strengthened conditions.

High-Temperature Performance

At elevated temperatures, A365 exhibits progressive strength loss as thermal activation allows dislocation recovery and grain boundary sliding; practical continuous-use limits are typically kept below ~150–200 °C for load-bearing applications. Oxidation is limited because aluminum forms a stable oxide, but prolonged exposure at higher temperatures or in aggressive atmospheres can alter surface chemistry and accelerate intermetallic coarsening, affecting ductility and fatigue. Welded zones and heavily cold-worked regions are more prone to property changes under thermal cycling because pre-existing dislocation structures and residual stresses relax, reducing localized strength.

For short-term elevated-temperature exposures (e.g., forming or brazing operations), designers should account for possible softening and dimensional change; long-term creep is minimal at moderate temperatures but can become significant if service temperatures approach 200–250 °C, especially under sustained loads.

Applications

Industry	Example Component	Why A365 Is Used
Automotive	Trim, housings, non-structural panels	Good formability, surface finish and corrosion resistance at reasonable cost
Marine	HVAC ducts and enclosures	Corrosion resistance and ease of fabrication for protected components
Aerospace	Interior fittings and non-critical brackets	Lightweight with good formability and acceptable mechanical performance
Electronics	Enclosures and heat spreaders	Good thermal conductivity and ability to be formed into complex shapes

A365 is useful where a balance of formability, corrosion resistance and modest strength is required. It is especially effective for manufactured parts that demand good surface quality and tight formed tolerances, but not the peak strength or fatigue life of high-strength heat-treated alloys.

Selection Insights

Choose A365 when the design priorities emphasize forming, corrosion resistance, and cost-effectiveness over maximum specific strength. It is an excellent choice for drawn, stamped or deep-formed components that will not be subjected to high sustained loads or aggressive stress-corrosion environments.

Compared with commercially pure aluminum (1100), A365 trades slightly reduced electrical and thermal conductivity for significantly improved strength and better dimensional stability during fabrication. Compared with work-hardened alloys such as 3003 or 5052, A365 typically sits with similar or marginally higher strength while maintaining comparable corrosion resistance and forming behavior. Compared with heat-treatable alloys like 6061 or 6063, A365 cannot reach the same peak strengths via aging, but it is preferred when extensive forming is required before final properties are needed or when better corrosion behavior and weldability with minimal post-weld treatment are desired.

Closing Summary

A365 remains relevant in modern engineering as a versatile, easy-to-fabricate aluminum alloy that balances good formability, acceptable mechanical performance and reliable corrosion resistance for many industrial, automotive and consumer applications. Its work-hardening response, combined with predictable thermal and mechanical behavior