Aluminum A380: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

A380 is a commercial die-casting aluminum alloy belonging to the Al-Si-Cu family rather than the classic wrought series such as 3xxx, 6xxx or 7xxx. It is typically categorized among Al–Si casting alloys (often referenced alongside ADC12/EN AC‑46000) and is formulated for high-volume die-casting applications where complex geometries and dimensional accuracy are required.

Major alloying elements are silicon (Si) in the eutectic-to-hypoeutectic range and copper (Cu) at levels sufficient to enable precipitation hardening; iron (Fe), magnesium (Mg) and trace titanium (Ti) and manganese (Mn) are present to control casting characteristics and microstructure. Strengthening is a mix of as-cast microstructure (eutectic Si and intermetallics), limited precipitation hardening from Cu/Mg, and some work-hardening effects produced by secondary operations; A380 is not a purely wrought, work-hardenable alloy.

Key traits of A380 include good castability, excellent dimensional stability in die-casting, moderate-to-high static strength for cast alloys, reasonable thermal and electrical conductivity for many enclosure and housing applications, and acceptable corrosion resistance for general atmospheric exposure. Weldability and formability are constrained compared with wrought aluminum grades; weld repair and post-cast heat treatment are possible but require process controls.

Typical industries using A380 are automotive (transmission cases, housings, brackets), consumer electronics (enclosures), small engine and pump housings, and general industrial cast components where geometry and economy matter. Engineers select A380 when a balance of castability, dimensional accuracy, adequate strength and low per-part cost outweigh the need for high ductility or high-temperature service performance.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O (Annealed)	Low	High	Good for limited forming	Good (with care)	Softened by furnace anneal; rarely used for final die-cast parts
As‑Cast (AC)	Moderate	Low–Moderate	Limited	Fair — porosity issues	Typical delivery condition from die casting; microstructure controls strength
T5 (Artificially aged)	Moderate–High	Low	Limited	Fair — filler choice critical	Often applied to improve mechanical properties without full solution treatment
T6 (Solution treated & aged)	High	Low	Poor	Challenging — HAZ softening	Achievable to increase strength, but risks distortion and porosity opening
H (cold worked, limited)	Moderate	Lower	Poor	N/A	Rare for die-castings; limited use where local deformation is applied

Temper affects A380 by shifting the relative balance of strength and ductility through microstructural changes and precipitation behavior. As‑cast material provides best dimensional fidelity from the die, T5 boosts strength with minimal distortion, and full T6 can maximize strength at the cost of increased processing, higher distortion risk, and limited gains because of casting porosity.

Chemical Composition

Element	% Range	Notes
Si	7.5–9.6	Primary alloying element controlling fluidity and shrinkage; forms eutectic/fine Si phases.
Fe	0.6–1.3	Impurity that forms intermetallics (β‑AlFeSi) affecting ductility and porosity tolerance.
Mn	≤0.35	Controls Fe intermetallic morphology; improves toughness marginally.
Mg	0.1–0.45	Contributes to age-hardening when combined with Cu; minor strengthening role.
Cu	1.5–3.5	Major contributor to precipitation hardening and strength after aging.
Zn	≤0.2	Low levels; minor solid solution strength contributor.
Cr	≤0.1	Trace levels to control grain structure and recrystallization in some variants.
Ti	0.02–0.2	Grain refiner used during melting to control as-cast grain size.
Others	Balance Al (plus trace Pb/Sn ≤0.05)	Aluminum is the balance; trace elements controlled for casting cleanliness.

The Si content controls casting characteristics—fluidity, feeding and shrinkage—and the size and morphology of Si particles influence both strength and fatigue resistance. Copper and magnesium permit precipitation strengthening during artificial aging, but the effectiveness of heat treatment is tempered by casting defects and intermetallic phases that reduce ductility and fatigue life relative to wrought alloys.

Mechanical Properties

A380 exhibits tensile behavior typical of mid‑range die casting alloys: relatively high ultimate strength for a casting with low-to-moderate yield and limited elongation. Tensile and yield values depend strongly on casting parameters, porosity levels, and temper; denser castings with controlled hydrogen and oxide entrainment show higher endurance and higher measured strengths.

Elongation is generally low compared with wrought aluminum; elongation-to-failure commonly sits in the 1–6% range for as‑cast and heat‑treated tempers, and ductility can be improved only modestly by annealing. Hardness correlates with temper and heat treatment — Brinell hardness increases from moderate values in the annealed condition to higher values after T5/T6 aging, but the presence of brittle intermetallics and coarse Si limits toughness and fatigue endurance.

Fatigue performance is sensitive to surface condition and casting defects; fatigue life is typically lower than for wrought alloys of comparable static strength and is improved by hot isostatic pressing, shot peening, or machining to remove surface defects. Thickness and section size influence cooling rates and microstructure; thin sections cool quickly producing finer microstructures and somewhat better mechanical properties, whereas thick sections are more susceptible to porosity and coarse eutectic structures.

Property	O/Annealed	Key Temper (As‑Cast / T5 / T6)	Notes
Tensile Strength (UTS)	135–220 MPa	250–340 MPa	Wide range due to casting practice and porosity; T5/T6 at upper range.
Yield Strength (0.2% offset)	55–125 MPa	110–210 MPa	T6 raises yield by precipitation; as‑cast yield varies with microstructure.
Elongation	4–12%	1–6%	Ductility is limited in cast forms; anneal helps but reduces strength.
Hardness (HB)	50–85 HB	75–110 HB	Hardness increases with artificial aging; local variability due to intermetallics.

Physical Properties

Property	Value	Notes
Density	~2.78 g/cm³	Slightly higher than pure Al due to Si/Cu/Fe content.
Melting Range	~500–575 °C	Partial melting/eutectic starts near eutectic temperature; solidus‑liquidus range due to alloying.
Thermal Conductivity	~90–120 W/m·K (25 °C)	Lower than pure Al because of Si and intermetallics; still good for housings and heat spreading.
Electrical Conductivity	~20–35 % IACS	Reduced relative to pure Al; conductivity falls with increased Cu/Si.
Specific Heat	~0.88–0.92 J/g·K	Typical for aluminum alloys; relevant for thermal management modeling.
Thermal Expansion	~21–23 µm/m·K	Similar to other Al–Si casting alloys; design for thermal mismatch in assemblies.

The physical property set makes A380 attractive for components that require dimensional stability, moderate heat dissipation and electrical grounding while keeping weight low. Thermal conductivity and specific heat make A380 suitable for moderate heat-sinking roles, but designers should account for the lower conductivity versus pure aluminum when heat dissipation is a primary function. Thermal expansion is typical for aluminum and must be accommodated in multi‑material assemblies to avoid thermal stress and galvanic degradation.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	Rarely supplied	Not typical	N/A	A380 is not commonly produced as wrought sheet; sheet applications use 5xxx/6xxx series.
Plate	Limited (thinner cast plates)	Variable with thickness	As‑Cast / T5	Some poured or thixocast plates exist but are uncommon; machining often required.
Extrusion	Not applicable	N/A	N/A	A380 is a casting alloy and is unsuitable for extrusion processes.
Tube	Rarely supplied	N/A	N/A	Tubular forms from die casting are very limited; welded tube from cast blanks sometimes used.
Bar/Rod	Casting bars/ingots for remelt	Similar to cast	As‑Cast	Supplied mostly as ingots or shot for die casting remelt, not as wrought bars for fabrication.

A380 is fundamentally a die‑casting alloy and its primary product form is cast components produced directly from high-pressure dies. Wrought forms such as sheet, plate and extrusions are uncommon because the alloy chemistry and casting microstructure are not optimized for wrought processing; manufacturers typically choose wrought alloys for those product forms. When functional needs require, castings are machined to final tolerances or combined with inserts and secondary operations rather than relying on forming.

Equivalent Grades

Standard	Grade	Region	Notes
AA	A380	USA	Common designation for die-casting industry and foundry specs.
EN AW	EN AC‑46000 (AlSi8Cu3(Fe))	Europe	Roughly equivalent; nomenclature emphasizes chemical family and Fe content.
JIS	ADC12	Japan	Widely referenced equivalent in Asia with similar Si/Cu content and casting behavior.
GB/T	AlSi9Cu (approx)	China	Local standards may list AlSi9Cu3 or similar as practical equivalents; chemistry may differ slightly.

Subtle differences among regional equivalents stem from allowed tolerances on Cu, Si and Fe plus permitted impurity levels and mechanical property test methods. ADC12 and EN AC‑46000 are frequently treated as near‑equivalents to A380 for design and procurement, but manufacturers should confirm chemical ranges, temporary heat‑treat options and mechanical-property certification before cross‑listing parts.

Corrosion Resistance

A380 has acceptable general atmospheric corrosion resistance driven by the native aluminum oxide film, and performs well in indoor, controlled environments where pitting agents are minimal. The presence of copper reduces overall corrosion resistance compared with low‑Cu wrought alloys; localized corrosion can occur particularly in chloride‑bearing environments and in areas with deposits that trap moisture.

In marine or high-chloride situations A380 exhibits higher susceptibility to pitting and crevice corrosion than 5xxx/6xxx wrought alloys that contain little or no copper; protective coatings and sealants are commonly specified for long‑term service. Stress corrosion cracking is not commonly reported for A380 in typical service, but the risk increases where tensile stresses, high chloride activity and elevated temperatures combine; designers should be conservative for structural marine applications.

Galvanic interactions make A380 anodic relative to many steels and copper alloys; when coupled in seawater or aggressive electrolytes, the aluminum component will corrode preferentially unless electrically isolated or protected by coatings and sacrificial anodes. Compared with other alloy families, A380 trades some corrosion resistance for castability and dimensional economy; if corrosion resistance is critical, choose low‑Cu alloys or protective systems.

Fabrication Properties

Weldability

Welding die‑cast A380 is feasible but presents challenges: porosity, entrained gases and oxides in die‑cast microstructures increase the risk of weld defects. TIG and MIG welding with Al‑Si filler wires (e.g., ER4043 or ER4047) are commonly recommended to match the silicon-rich base and reduce hot‑cracking tendency; ER5356 may be used for higher strength but increases susceptibility to cracking in Al–Si castings. Preheating to 150–200 °C, grinding to sound metal, and post‑weld heat treatments or peening can improve weld-quality; however, HAZ softening and porosity opening often limit repair strength.

Machinability

A380 is considered reasonably machinable for a casting alloy; the eutectic Si particles reduce built-up edge and promote chip breakage, while the alloy’s moderate hardness allows higher feed rates than softer pure Al. Carbide tooling with positive rake geometry and adequate coolant is standard for high‑volume machining; cutting speeds are similar to other Al alloys but tool life is influenced by Si content and abrasive intermetallics. Fine surface finishes require control of feed and tool geometry to avoid chatter and pull‑out of silicon particles.

Formability

Forming A380 is limited because castings are not ductile like wrought aluminum. Bend radii must be conservative and localized forming operations often result in cracking or fracture due to low elongation; designers typically avoid heavy cold forming of A380 castings. Best forming outcomes come from designing features into the die, using inserts, or selecting more ductile wrought alloys for post‑forming requirements; annealing can improve ductility but reduces strength significantly.

Heat Treatment Behavior

Although A380 contains Cu and Mg enabling some precipitation hardening, heat‑treatment response is constrained by the as‑cast microstructure and porosity. Solution heat treatment is performed at temperatures typically around 495–540 °C to dissolve soluble phases, followed by rapid quenching and artificial aging at 150–200 °C to precipitate strengthening phases; this produces T6 or T5 conditions depending on whether full solution is used.

Practical limitations include distortion, opening of porosity and oxide films during solution treatment which can reduce dimensional accuracy and fatigue life; many die‑casting manufacturers therefore prefer T5 (direct aging) or control‑aged processes to balance strength gains against shape stability. For non‑heat‑treatable behavior, A380 can be softened by furnace annealing to increase ductility for limited forming, and local cold working will increase hardness slightly but is not a substitute for full wrought alloys.

High-Temperature Performance

A380’s strength degrades with temperature and the alloy is generally recommended for continuous service below roughly 150 °C for load‑bearing applications. Elevated temperature service accelerates softening of age‑hardened structures and can promote coarsening of precipitates, reducing both static strength and fatigue life; prolonged exposures above ~200 °C are not typical for A380 components. Oxidation of aluminum is generally protective, but at higher temperatures intermetallics and differential expansion can cause microcracking and reduce sealing integrity in assemblies.

Welded or repaired sections develop HAZ regions where overaging or softening occurs; high temperature excursions can exacerbate HAZ softening and reduce load path capacities, so designers must account for reduced local strength and avoid placing critical bolted or welded joints in high‑temperature zones.

Applications

Industry	Example Component	Why A380 Is Used
Automotive	Transmission housings, valve body housings, brackets	Excellent die-castability, dimensional accuracy, cost-effective for high-volume parts
Marine