Aluminum A413: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A413 is best classified within the 4xxx-series aluminium family, a silicon-rich group optimized for casting fluidity, low shrinkage, and weld filler applications. Its major alloying elements are silicon as the primary constituent (providing eutectic formation and fluidity), with controlled additions of copper and modest amounts of magnesium and manganese to enable strength and age-hardening response in certain variants.

The alloy’s strengthening mechanisms combine microstructural control of the Al-Si eutectic (refinement, morphology) with precipitation hardening when copper and magnesium levels are sufficient for engineered heat treatment sequences. Depending on product form and temper, A413 can be supplied in an annealed, artificially aged (T5/T6), or stress-relieved condition, giving designers a range from very ductile to moderately high-strength states.

Key traits of A413 include good castability and thermal conductivity relative to many other Al alloys, reasonable corrosion resistance in atmospheric conditions, and acceptable machinability owing to its silicon content. Weldability can be good with appropriate filler alloys, but the presence of copper elevates susceptibility to localized corrosion and reduces weld-related ductility compared with low-alloyed commercial-pure Al.

Industries commonly using A413 include automotive (transmission housings, pump bodies, brackets), powertrain and general mechanical components, electrical and thermal management parts (heat sinks, housings), and consumer appliances where cast or extruded shapes with moderate strength and high dimensional stability are required. Engineers specify A413 to balance castability and post-cast heat-treatable strength while keeping density low and thermal performance acceptable compared with higher-strength, more expensive wrought alloys.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (8–20%)	Excellent	Excellent	Fully annealed, best for forming and stress relief
T5	Medium	Moderate (4–10%)	Good	Good	Artificially aged from an as-cast or cooled-from-casting condition
T6	High	Low–Moderate (2–8%)	Fair	Requires care	Solution treated and artificially aged to maximize strength
T651	High	Low–Moderate (2–8%)	Fair	Requires care	Solution treated, stress-relieved by stretching, then artificially aged
H14 (work-hardened)	Medium	Moderate (4–10%)	Limited	Good	Applicable to wrought product; increases yield via cold work

Temper selection for A413 strongly influences the microstructure and therefore property trade-offs: annealed conditions provide the best ductility and formability, while T6/T651 maximize yield and tensile strength at the expense of elongation. Artificial aging temperatures and times (T5 vs T6) control precipitate size and distribution in Al–Si–Cu variants, so design engineers must consider required performance after service and any post-processing such as welding.

Metallurgical condition also interacts with section thickness and casting method: thin sections reach intended tempers more uniformly during heat treatment, whereas thicker castings may require extended solution times or exhibit coarser eutectic structures that reduce effective strength. Selecting a temper is therefore a multi-parameter decision tied to component geometry, required fatigue life, and downstream fabrication steps.

Chemical Composition

Element	% Range	Notes
Si	9.0–13.0	Primary strengthening and fluidity element; controls eutectic fraction and reduces shrinkage
Fe	0.4–1.5	Impurity-forming intermetallics (β-Al5FeSi); adversely affects ductility and fatigue
Mn	0.2–0.8	Modifies iron intermetallics; improves hot-tearing resistance and strength modestly
Mg	0.1–0.6	Enables Al–Mg–Si/Cu precipitation and contributes to age-hardening response
Cu	1.0–3.0	Principal contributor to precipitation hardening and elevated strength after T6 treatments
Zn	≤0.3	Minor, usually incidental; higher Zn can marginally increase strength but may compromise corrosion resistance
Cr	≤0.25	Grain structure control and stabilization during thermal cycles
Ti	≤0.2	Grain refiner in castings and extrusions
Others	≤0.15 total	Trace elements (Ni, Pb, Sn) usually limited; certain impurities can affect machinability and castability

The chemical balance in A413 is designed to prioritize silicon-driven castability while retaining an amount of Cu and Mg sufficient for precipitation strengthening in heat-treated conditions. Silicon controls fluidity and eutectic morphology; copper and magnesium permit T6-style strengthening by forming fine intermetallic precipitates on aging. Iron and other impurities tend to form brittle phases that reduce fracture toughness and fatigue life, so tight composition control and exclusion practices during melting/casting improve component performance.

Mechanical Properties

A413 exhibits a wide band of tensile behavior that depends strongly on temper and casting quality. In annealed/cast–annealed (O) condition, tensile strengths are modest with relatively high elongation driven by a fine primary aluminium matrix and ductile eutectic silicon morphology. After solution-treatment and aging (T6-type sequences), copper and magnesium precipitates raise yield and ultimate strengths significantly, but ductility is reduced and toughness can become sensitive to casting defects and porosity.

Yield strength typically increases from a low-plateau in the annealed state to much higher values when aged; the exact elevation depends on copper content and aging parameters. Hardness tracks tensile properties and can be used as a quick shop-floor proxy for temper uniformity. Fatigue performance is strongly dependent on surface finish, porosity levels, and the presence of coarse intermetallics; cast A413 requires careful process control to achieve robust fatigue life.

Thickness effects are important: thicker sections cool slower, promoting coarser Si particles and larger intermetallics, which reduce strength and elongation compared with thin-wall castings or extruded sections. Machining-induced features and thermal cycles from welding can locally soften aged conditions, creating heterogeneous zones that require post-weld heat treatment or design allowances.

Property	O/Annealed	Key Temper (T6)	Notes
Tensile Strength (UTS)	140–220 MPa (typical)	300–380 MPa (typical)	Wide range depends on casting quality, section thickness, and exact Cu/Mg levels
Yield Strength (0.2% offset)	70–140 MPa	200–300 MPa	T6 delivers the largest increase in yield via precipitate strengthening
Elongation (in 50–200 mm gauge)	8–20%	2–8%	Ductility decreases substantially after aging; thin sections show higher elongation
Hardness (HB)	30–60 HB	80–120 HB	Brinell hardness correlates to aging condition and Si morphology

Physical Properties

Property	Value	Notes
Density	2.68–2.72 g/cm³	Typical aluminium density; varies slightly with alloying content
Melting Range	~575–615 °C (solidus–liquidus typical)	Eutectic Al–Si alloys have a lower solidus and benefit from a narrow freezing range in casting
Thermal Conductivity	120–180 W/m·K (approx.)	Reduced from pure Al by Si and Cu additions; still suitable for many thermal management uses
Electrical Conductivity	25–45 % IACS (approx.)	Lower than pure Al due to solute scattering from Si and Cu
Specific Heat	~880–910 J/kg·K	Comparable to wrought aluminium alloys; useful for thermal mass calculations
Thermal Expansion	21–24 µm/m·K (20–200 °C)	Typical coefficient for Al–Si alloys; design for differential expansion in assemblies

A413 retains much of the favourable physical profile of aluminium: low density and good thermal conductivity relative to many structural metals. Silicon additions lower electrical and thermal conductivity from the values of high-purity aluminium but improve castability and dimensional stability during solidification. The alloy’s melting and solidification behavior, driven by the Al–Si phase diagram, make it well-suited to die casting, sand casting, and other liquid-metal shaping processes.

Thermal expansion of A413 must be accounted for in assemblies that join dissimilar materials, particularly where thermal cycling is frequent. Heat capacity and conductivity values make A413 attractive for components requiring heat spreading combined with reasonable mechanical strength after heat treatment.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.5–6 mm	Moderate (depends on processing)	O, H14, T6	Wrought processing required for thin gauge; often limited for high-Si alloys
Plate	6–50+ mm	Variable; thicker plate tends to be coarser	O, T6	Plate used where castings are not required; thickness affects heat-treat response
Extrusion	2–60 mm sections	Good when composition tailored for extrusion	O, T6, T651	Requires modification for extrusion (Ti, Mg control); good for structural profiles
Tube	1–25 mm wall	Dependent on forming method	O, T6	Seamless or welded tubes possible; heat treatment used for strength control
Bar/Rod	≤200 mm dia	Wrought bars exhibit better mechanical consistency	O, T6	Used for machining blanks and forgings; grain control via thermomechanical processing

Product form strongly affects the achievable microstructure and therefore mechanical behavior. Castings are the most common form for high-Si A413, benefitting from silicon’s improvement of fluidity and reduced shrinkage, while wrought products (extrusions, plates) require adjustments to composition for hot-workability and grain control. Heat treatment protocols and mechanical processing (rolling, stretching) differ by form; designers must account for residual stresses, porosity in castings, and anisotropy in extruded profiles.

Selecting product form is often dictated by component geometry and production volumes: die casting for complex thin-walled shapes, sand casting for heavy or low-volume parts, and extrusion/wrought for long profiles where surface finish and dimensional tolerances are critical. Each form has distinct inspection and quality-control requirements to mitigate casting defects and ensure predictable mechanical performance.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A413	USA	Aluminium Association-style designation for the Al–Si–Cu family; used as a commercial identifier
EN AW	AlSi12Cu (approx.)	Europe	Common EN designation for analogous composition used in die casting and general castings
JIS	ADC12 (approx.)	Japan	ADC12 is a widely used Japanese die-casting alloy similar in composition and properties
GB/T	AlSi12Cu (approx.)	China	Chinese standards use Al–Si–Cu nomenclature; similar casting practices and temper definitions

Equivalency between standards is approximate because each organization specifies slightly different element limits and permitted impurities, plus different processing and testing protocols. For critical applications, engineers should compare certified chemical analysis, heat-treatment schedules, and mechanical test certificates rather than rely solely on nominal grade names. Differences in allowable iron, manganese, and trace elements can significantly affect fatigue and fracture behaviour.

Corrosion Resistance

A413 provides generally good atmospheric corrosion resistance due to the protective aluminium oxide film; the silicon content does not itself significantly harm general corrosion performance. In mildly corrosive industrial atmospheres the alloy performs comparably to other Al–Si families, but elevated copper content can promote localized galvanic effects and reduce resistance to pitting in chloride-containing environments.

Marine exposure is more challenging: chloride-induced pitting and crevice corrosion risks are elevated, especially in aged or anodically active conditions. Copper-containing Al alloys can sustain faster localized attack relative to low-copper alloys; therefore, protective coatings, anodizing, or cathodic protection are commonly specified for long-term marine service. Design for drainage, reducing crevices, and specifying protective finishing markedly improves longevity.

Stress corrosion cracking (SCC) is less prevalent in Al–Si–Cu cast alloys than in certain high-strength Al–Zn–Mg families, but tensile-stressed, sensitized regions (e.g., weld HAZ with residual tensile stresses) may exhibit susceptibility in aggressive chloride environments. Galvanic interactions with dissimilar metals must be addressed: in direct contact with stainless steels the galvanic effect is modest, but with carbon steel the aluminium will corrode preferentially if coatings or insulators are not used.

Compared with other alloy families, A413 offers superior castability and thermal performance at the expense of the highest possible corrosion resistance; alloys in the 5xxx series (e.g., 5052) give better marine corrosion resistance, while 6xxx series offer a different balance of strength and corrosion behavior after anodizing.

Fabrication Properties

Weldability

Welding of A413 is feasible with standard TIG and MIG/GMAW processes when appropriate filler alloys (Al-Si or Al-Si-Cu fillers) are used to match base-metal properties. Heat input management is critical to minimize porosity and to reduce HAZ softening in T6 conditions; pre- and post-weld heat treatments can be required for critical structural parts. Hot-cracking risk is moderate due to silicon-rich eutectic; use of clean base metal and controlled joint design reduces susceptibility.

Machinability

The relatively high silicon content in A413 produces an abrasive phase that increases tool wear but imparts positive chip breaking behavior and dimensional stability. Typical machinability is rated moderate: carbide tooling and rigid setups with conservative speeds are recommended for high material removal rates. Coolant and chip evacuation are important to avoid built-up edge and to maintain surface finish; coatings or carbide grades optimized for aluminium–silicon alloys are preferred.

Formability

Formability is best in annealed tempers; cold forming of high-silicon compositions is limited by the brittle nature of coarse eutectic silicon and intermetallic particles. Bend radii should be increased relative to ductile 5xxx to avoid cracking; pre-heating and warm forming can improve formability for complex shapes. For wrought variants, H tempers provide room-temperature forming capacity, while T6 parts are typically formed only by limited, incremental processes or require recrystallization annealing.

Heat Treatment Behavior

A413 behaves as a heat-treatable Al–Si–Cu-based alloy when copper and magnesium levels are sufficient to support precipitation hardening. Solution treatment is typically performed at approximately 500–540 °C to dissolve soluble phases and homogenize the microstructure, followed by rapid quenching to retain a supersaturated solid solution. Artificial aging (T5 or T6 regimes) at 150–200 °C precipitates fine Cu- and Mg-rich phases to raise strength; aging schedule controls peak strength vs overaging sensitivity.

T5 is often used for castings where material is artificially aged from the as-cast condition without prior full solutioning; this gives moderate strength with better dimensional stability. T6 involves full solution treatment, quench, and aging and achieves the highest practical strength for the alloy, but requires careful control to avoid distortion and thermal stress. Overaging reduces strength but improves toughness and corrosion resistance; engineers may deliberately overage in some applications to trade peak strength for better durability.

For non-heat-treatable variants or where thermal cycles are impractical, work hardening (H-series tempers) and annealing (O) remain the primary methods to manipulate properties. Annealing removes residual stresses and restores ductility, while controlled cold work provides modest strength increases without altering chemical composition.

High-Temperature Performance

A413 experiences progressive strength loss as service temperatures increase beyond typical ambient conditions; long-term use above approximately 150–200 °C accelerates precipitate coarsening and reduces yield and tensile strength. Thermal exposure near the solution treatment range will dramatically alter mechanical properties and can lead to permanent softening, so thermal limits must be respected in design.

Oxidation is not typically a limiting factor because aluminium forms a thin, protective Al2O3 layer, but elevated temperatures accelerate scale formation and can alter thermal contact resistance. HAZ regions around welds can be particularly susceptible to softening during high-temperature exposure; design and material selection should consider post-weld heat treatment or mechanical compensation if high-temperature performance is required.

Creep resistance of A413 is limited compared with high-temperature aluminium alloys; for sustained high-temperature loads, alternative alloys with engineered creep resistance or metallic substitutes should be considered. Short-term exposure to elevated temperatures (intermittent thermal spikes) is usually tolerable provided adequate margins are applied.

Applications

Industry	Example Component	Why A413 Is Used
Automotive	Transmission housings, pump bodies	Good castability, dimensional stability, and heat-treatable strength
Marine	Valve bodies, fittings	Reasonable corrosion resistance and good cast productivity with protective finishes
Aerospace (secondary)	Brackets, housings, non-primary structures	Favorable strength-to-weight and thermal conductivity for secondary structures
Electronics	Heat sinks, enclosures	Thermal conductivity and ease of casting complex shapes
Consumer Appliances	Compressor housings, motor brackets	Cost-effective casting and post-cast strength via T5/T6 aging

A413 is chosen for components that require complex shapes produced economically through casting or extrusion while allowing post-process heat treatment to achieve the necessary mechanical properties. Its balance of manufacturability, thermal performance,