Aluminum ADC12: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

ADC12 is a high-silicon, copper-containing aluminum alloy classified within the cast alloy family and commonly referenced under JIS (Japanese Industrial Standards) as ADC12. It is not part of the wrought 1xxx–7xxx series nomenclature, but is best described as an Al-Si-Cu casting alloy developed for pressure die casting and sand casting applications.

Major alloying elements are silicon (Si) at relatively high levels, copper (Cu) in moderate quantities, with iron (Fe) and small additions of manganese (Mn), magnesium (Mg), zinc (Zn) and trace elements such as titanium (Ti) and chromium (Cr). The high silicon content forms a hard eutectic/primary silicon phase that contributes to strength and wear resistance while copper provides additional age-hardening and elevated-temperature strength.

ADC12 primarily strengthens by a combination of microstructural control (Si eutectic and intermetallic phases) and limited precipitation hardening from Cu-bearing phases after solution treatment and artificial aging. The alloy exhibits good as-cast strength for lightweight structural components, moderate corrosion resistance, reasonable thermal and electrical conductivity for its class, and acceptable machinability; formability and weldability are more constrained relative to wrought aluminum alloys.

Typical industries using ADC12 include automotive (dies, housings, transmission cases, brackets), consumer appliances, electrical enclosures, and some marine and general industrial cast components. Engineers select ADC12 when a cost-effective die-castable material is required that balances castability, dimensional stability, mechanical strength, and machinability for medium-duty, high-volume components.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
F (As-cast/As-fabricated)	Low–Medium	Low–Moderate	Limited	Poor–Moderate	Standard die-cast condition with typical porosity and eutectic microstructure
O (Annealed)	Low	Higher	Improved	Moderate	Rare for ADC12; improved ductility at cost of strength
T5 (Artificially aged after cooling from casting)	Medium–High	Low–Moderate	Limited	Poor–Moderate	Common for die-cast components to stabilize dimensions and increase strength
T6 (Solution treated + artificial aging)	High	Low	Poor	Poor	Achieves higher strength if parts can be solution-treated and quenched effectively
T4 (Solution treated + naturally aged)	Medium	Low–Moderate	Limited	Poor	Less common due to difficulty achieving full solutionizing in complex castings

Temper notably shifts mechanical performance and practical usability in die cast parts. As-cast and T5 conditions are most common in industrial practice because they balance dimensional stability, residual stresses and achievable strength without requiring complex heat treatment of large cast assemblies.

When T6 or solution-based tempers are pursued, gains in tensile and yield strength are possible but are strongly dependent on section thickness, porosity, and the ability to obtain uniform solutionizing and quench rates; thin-walled die castings may not respond uniformly to T6 treatment.

Chemical Composition

Element	% Range	Notes
Si	10.0 – 13.0	Primary alloying element; forms eutectic silicon and hard phases that improve strength and wear resistance
Fe	0.6 – 1.3	Impurity that forms intermetallics; excessive Fe reduces ductility and increases brittleness
Mn	0.05 – 0.45	Controls some intermetallic morphology; small additions refine grain structure
Mg	0.05 – 0.45	Low levels; can contribute to minor solid solution strengthening and aging response
Cu	2.0 – 3.5	Promotes precipitation strengthening and higher temperature strength; reduces corrosion resistance
Zn	≤ 0.25	Typically a minor impurity; higher Zn not common in ADC12
Cr	≤ 0.10	Grain structure modifier; limits hot tearing in some castings
Ti	≤ 0.20	Grain refiner used in melting practice and ingot production
Others (Ni, Pb, Bi, Sr, Zr)	Balance to specified limits	Trace additions or impurities controlled per spec; Al balance typically > 85%

The alloy chemistry places Si and Cu as the key performance drivers: silicon provides a hard eutectic network and improves fluidity during casting, while copper enables additional precipitation strengthening after heat treatment. Iron and other impurities influence the morphology of intermetallics and thus affect ductility and fatigue resistance. Alloying is balanced to optimize die fill, minimize hot-tearing, and produce a microstructure that machines and ages predictably.

Mechanical Properties

ADC12 exhibits tensile behavior that is highly dependent on casting method, section thickness, porosity, and heat treatment. Die-cast ADC12 in typical as-cast or T5 conditions displays moderate-to-high tensile strength for a cast aluminum (commonly in the 200–300 MPa range) with relatively low ductility compared with wrought alloys. The brittle nature of the Si-rich microstructure limits elongation, particularly in thicker sections where porosity and shrinkage play a role.

Yield behavior follows tensile performance; ADC12 can develop appreciable yield strength in T5/T6-like conditions due to Cu-containing precipitates and microstructural aging. Hardness increases significantly from annealed to aged conditions as the Cu phases and refined Si distribute through the matrix. Fatigue performance is influenced by casting defects and intermetallics; surface finish, porosity and heat treatment all strongly control endurance limits.

Thickness has a pronounced effect because cooling rate during solidification controls silicon particle size, porosity levels and the ability to achieve uniform solution treatment. Thin sections typically attain higher strength and lower porosity but can be more prone to hot tearing during casting.

Property	O/Annealed	Key Temper (e.g., T5/T6)	Notes
Tensile Strength (MPa)	120 – 160	200 – 300	Wide range due to casting process, porosity, and section thickness
Yield Strength (MPa)	60 – 110	160 – 240	Higher in aged conditions with Cu precipitation; yield varies with section and defects
Elongation (%)	4 – 10	1 – 6	Elongation drops as strength increases; brittle Si phases limit ductility
Hardness (HB)	40 – 70	80 – 120	Hardness increases with artificial aging and solution treatment

Physical Properties

Property	Value	Notes
Density	2.75 – 2.80 g/cm³	Typical for Al-Si casting alloys; component mass advantage over steel
Melting Range	Solidus ~ 510 – 540 °C, Liquidus ~ 560 – 585 °C	Broad melting/solidification interval due to alloying and eutectic behavior
Thermal Conductivity	~100 – 130 W/m·K	Lower than pure Al but adequate for many thermal management applications
Electrical Conductivity	~20 – 35 % IACS	Reduced by Si and Cu compared with pure aluminum
Specific Heat	~0.88 – 0.92 J/g·K	Comparable to other aluminum alloys for transient thermal calculations
Thermal Expansion	~22 – 24 µm/m·K	Typical aluminum expansion; consider for tight tolerance assemblies

ADC12’s physical properties make it attractive where light weighting and castability are priorities. Density advantages allow mass savings versus ferrous materials while thermal and electrical conductivities, though reduced from pure aluminum, remain useful in housings and certain thermal applications. The melting range and solidification characteristics govern die design, gating, and cooling strategies during casting.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	Limited availability; thin gauges uncommon	Not typical; properties variable	O, T5 (if produced)	ADC12 is rarely supplied as cold-rolled sheet; cast-derived sheets have limited ductility
Plate	Limited; typically cast plates	Variable with thickness and heat treatment	O, T5/T6	Thick cast plates have greater porosity and lower toughness
Extrusion	Not typical	N/A	N/A	ADC12 is not normally used for extrusion; wrought alloys are preferred
Tube	Limited (cast tubes or fabricated)	Variable	O, T5	Tubular forms are rare; manufacturing often by secondary fabrication
Bar/Rod	Machined bars from ingots; forgings rare	Good machinability when solid material	O, T5	Commonly supplied as castings or machined billets for secondary operations

ADC12 is predominantly produced as die-cast and sand-cast components rather than conventional sheet, plate or extruded products. Die casting enables thin-walled, complex geometries with close tolerances and surface finish suitable for many industrial parts. Secondary processing such as machining, heat treatment and surface finishing is often applied to meet final product requirements.

Processing differences map directly to application suitability: die-casting provides high productivity and geometric complexity; sand casting can produce larger parts but with lower mechanical performance and higher porosity; wrought processes are generally not used because ADC12’s composition and microstructure are optimized for casting.

Equivalent Grades

Standard	Grade	Region	Notes
AA (Aluminum Association)	A383 / A413 (approx.)	USA	A383/A413 are Al-Si-Cu casting alloys with compositions and properties broadly similar to ADC12
EN AW	EN AC-AlSi12Cu1(Fe) (approx.)	Europe	European casting designation corresponds to ~12% Si, ~1% Cu family; exact limits vary by spec
JIS	ADC12	Japan	JIS standard designation for this specific die-casting alloy
GB/T	ZL102 / AlSi12Cu (approx.)	China	Chinese cast Al-Si-Cu grades are similar but vary in impurity and trace element controls

Equivalent designations approximate the composition family rather than being exact chemical twins. Differences between regions are typically in allowable impurities, exact Cu and Fe limits, and process-related quality controls (porosity, cleanliness). Engineers must review specific standard sheets and batch certificates when substituting between JIS ADC12 and regional equivalents to ensure critical element and mechanical property alignment.

Corrosion Resistance

ADC12 provides moderate atmospheric corrosion resistance typical of Al-Si casting alloys; a protective aluminum oxide film forms naturally and offers primary defense against uniform corrosion. However, the presence of copper reduces corrosion resistance relative to near-pure aluminum or Mg-containing 5xxx series alloys, particularly in chloride-containing environments where localized pitting can occur.

In marine or high-salinity exposures, ADC12 can develop pitting and crevice corrosion, especially on cast surfaces with porosity or intermetallic clusters that act as initiation sites. Protective coatings, sealants, or anodizing (where feasible) are commonly employed when marine exposure is expected.

Stress corrosion cracking is not a primary failure mode for ADC12 in most service conditions, but components under sustained tensile stress in corrosive atmospheres can show accelerated localized degradation due to Cu-containing phases. Galvanic behavior places ADC12 anodic to many common engineering metals; isolation from cathodic materials like stainless steel is advised or design adjustments made to expose minimal bimetallic contact. Compared with 5xxx and 6xxx wrought families, ADC12 trades some corrosion robustness for casting performance and machinability.

Fabrication Properties

Weldability

Welding of ADC12 is generally challenging because typical die-cast microstructures contain porosity and eutectic silicon that promotes hot-cracking and lack-of-fusion defects. TIG and MIG welding can be used for repairs or fabrication when porosity is low, but many practitioners eschew full structural welds in favor of mechanical fastening or adhesive bonding. When welding is required, Al-Si filler alloys (e.g., ER4043) are commonly recommended to mitigate hot-cracking and to provide compatible metallurgical transitions. Preheating, good joint fit-up, and post-weld heat treatment strategies can reduce residual stresses and cracking risk, but HAZ softening and compromised integrity near welds remain concerns.

Machinability

ADC12 is regarded as a good-to-excellent machinable casting alloy because the hard silicon particles help produce short, breakable chips and reduce built-up edge formation. Carbide tooling with TiAlN or similar coatings at moderate turning speeds is typical; feed and depth of cut depend on section thickness and porosity. Surface finish is generally good for die-cast components, but attention to burr control and tool path is necessary to avoid tearing fragile eutectic regions. Coolant application reduces built-up edge and prolongs tool life in high-volume machining.

Formability

Forming operations are limited for ADC12 due to the brittle nature of its silicon-rich microstructure and the presence of porosity in cast parts. Bend radii must be relatively large and forming should be performed on annealed (O) condition material where available, though fully annealed ADC12 is not commonly supplied. Cold working produces limited work-hardening benefit; hence forming strategies typically rely on designing cast geometries to final shape rather than heavy post-casting deformation.

Heat Treatment Behavior

ADC12 exhibits limited but useful response to heat treatment, primarily through solution treatment, quenching and artificial aging sequences that target copper-containing precipitates. Typical solution treatment temperatures are in the 480–535 °C range to dissolve soluble phases, followed by rapid quenching to retain a supersaturated solid solution; artificial aging at 150–200 °C then precipitates strengthening Cu-rich phases that raise yield and tensile strength. Achieving uniform solutionizing and quench rates is difficult in complex, thick castings, so heat treatment benefits are most realized in thin-walled or solid components prepared to heat-treatment-friendly geometries.

For many production applications, ADC12 is given a T5-type treatment—artificial aging without full solutionizing—because it provides dimensional stability and moderate strength gains with less distortion risk. Complete T6 treatment is possible but is limited in practice by cast porosity, trapped gases, and the potential for distortion; the overall hardening response is also less dramatic than in high-strength wrought heat-treatable alloys due to the dominant influence of the silicon eutectic. For non-heat-treated processing, work hardening is minimal and conventional annealing can raise ductility while lowering strength for limited forming operations.

High-Temperature Performance

ADC12 loses strength progressively with increasing temperature; above approximately 125–150 °C long-term structural strength declines noticeably as precipitates coarsen and the matrix softens. Short-term elevated-temperature exposure up to 200–250 °C can be tolerated depending on load and required safety margins, but sustained loading at these temperatures is not recommended for structural components. Oxidation at elevated temperatures is modest because aluminum forms a protective oxide, although surface degradation and scale can occur in aggressive atmospheres.

The HAZ near welds and heat-treated zones can show softening or embrittlement depending on thermal cycles; copper-containing intermetallics tend to coarsen under prolonged heat. For high-temperature applications, alternative alloys (e.g., Al-Si-Mg or specialized high-temperature aluminum or non-aluminum alloys) should be considered when service temperatures exceed ADC12’s practical limits.

Applications

Industry	Example Component	Why ADC12 Is Used
Automotive	Transmission housings, valve bodies, brackets, covers	Excellent die-castability for complex geometry, balance of strength and machinability for mass production
Consumer Appliances	Motor housings, frames	Good surface finish and dimensional control for aesthetic and functional parts
Electronics	Enclosures, connectors	Adequate thermal conductivity and EMI shielding