Cast aluminum specification comes down to four binding choices: alloy family, casting process, required mechanical/thermal class, and corrosion environment, with the Al-Si system serving as the basis for the most popular cast aluminum alloys—including the gravity-cast A319 and A356 grades, which account for most industrial applications—per metallurgical reference [S1].
Two gravity-cast alloys, A319 (Al-6Si-3Cu-1Fe-1Zn) and A356 (Al-7Si-0.25Cu-0.2Fe-0.4Mg), carry the bulk of automotive and industrial structural castings, while A380 (Al-8.5Si-3.5Cu-3Zn) and A383 (Al-10.5Si-2.5Cu-3Zn) are the workhorses for high-pressure die casting (HPDC) of covers, housings, and thin-wall structural parts [S1]. The full cast-alloy universe is split across Aluminum Association (AA) and EN 1780 designations, covering 1xx.x unalloyed through 7xx.x Al-Zn systems, with the 3xx.x Al-Si+Mg/Cu family alone spanning more than 90% of tonnage poured in most foundries [S1]. For context on how cast aluminum compares with its wrought counterpart, see the cast iron reference, which traces the historical divide between cast and wrought metallurgy.
Alloy Family Map: 1xx.x Through 7xx.x Per AA/EN 1780
Cast aluminum alloys group into four principal systems plus unalloyed Al: Al-Si (3xx.x / EN 40000 family including 4xx.x binary), Al-Cu (2xx.x / EN 20000), Al-Mg (5xx.x / EN 50000), and Al-Zn (7xx.x / EN 70000), with unalloyed ≥99% Al as 1xx.x / EN 10000 used almost exclusively for electrical conductivity [S1].
Al-Cu alloys such as AlCu4MgTi (AA 204.0) and AlCuMnMg (AA 203.0) deliver the highest strength and highest operating temperature in the cast family, but they sacrifice castability and corrosion resistance, restricting them to aerospace, military, and high-temperature structural castings [S1]. Al-Mg 5xx.x alloys give the best corrosion performance and are routinely specified for marine hardware, food-contact parts, and anodized architectural castings where the as-cast surface finish must double as the final finish.
Gravity Casting vs HPDC: A356/A319 Against A380/A383
For sand and permanent-mold gravity castings, A356 and A319 account for most industrial applications, with A356 (Al-7Si-0.25Cu-0.2Fe-0.4Mg) preferred when weldability, ductility, and T6/T7 heat-treatment response are required, and A319 (Al-6Si-3Cu-1Fe-1Zn) preferred when higher as-cast hardness and machinability outweigh the corrosion penalty from 3% Cu [S1].
For HPDC, A380 (Al-8.5Si-3.5Cu-3Zn) is the default non-structural alloy for covers, cases, and housings, while A383 (Al-10.5Si-2.5Cu-3Zn) trades some fluidity for higher strength in structural and more demanding HPDC parts [S1]. Chinese foundries such as the Foshan-based supplier active on the B2B marketplace offer in-house mould and CNC support across these four alloys for lamp shells, auto accessories, furniture legs, and pump/cylinder housings [S2]. The same selection logic carries into linear guide carriage housings and pump end-covers, where A380 HPDC keeps cycle times under 90 seconds for thin-wall parts while A356 sand casting carries thicker sections up to 50 mm without hot-tear rejection.
New-Generation Structural Alloys: AURAL-2, Silafont-36, Magsimal-59
Three recent alloys, AURAL-2 (Al-10Si-0.4Mg-0.5Mn), Silafont-36 (Al-10Si-0.3Mg-0.6Mn), and Magsimal-59 (Al-5Mg-2Si-0.5Mn), were developed specifically for automotive body structural castings that need high strength combined with high ductility, and all three cap Fe at <0.2%, which excludes most secondary alloy feedstock and pushes unit cost above conventional A319 and A380 [S1].
The low-Fe ceiling is not arbitrary: Fe forms brittle Al-Fe-Si needles that act as crack initiators under crash loading, and the new-generation alloys instead use Mn (0.5–0.6%) to convert the iron into a more rounded Chinese-script or α-phase morphology that is far less damaging to elongation. Aural-2 and Silafont-36 are vacuum or low-pressure die-cast into thin-wall shock towers, battery enclosures, and rear longitudinal rails; Magsimal-59 is a non-heat-treated Al-Mg-Si variant aimed at parts that must reach ≥12% elongation in the as-cast condition. Relative to A356-T6 baseline tensile properties, the new alloys developed for automotive body structural applications typically deliver higher yield strength with comparable or better ductility, the trade-off being higher per-part raw-material cost and a much narrower secondary-feedstock supply pool, since these alloys specify very low Fe content limits (<0.2%) that restrict the use of secondary alloy per [S1].
Selection Criteria Matrix: Family × Process × Property × Environment
Cast aluminum selection should be locked in this order: (1) casting process, (2) alloy family, (3) temper/heat treatment, (4) corrosion class, with each axis narrowing the available choices before the next is decided [S1].
Engineers can shortlist in three steps. First, process: HPDC rules out heat-treatable alloys because trapped gas blisters at solution treatment, pushing the choice to A380/A383 or to vacuum-assist HPDC with Aural-2/Silafont-36; sand or gravity die casting opens the full A356/A319/206/242.0 range. Second, environment: marine or food-contact specs default to 5xx.x Al-Mg (e.g. 514.0, 535.0) or to low-Cu 3xx.x (A356 with Cu ≤0.25%); high-temperature service above 200°C pulls the selection toward 2xx.x (203.0, 204.0, 242.0). Third, mechanical class: A356-T6 delivers roughly 230–260 MPa ultimate tensile with 6–10% elongation, A319-T5 sits 10–15% lower, A380-F (as-cast HPDC) is around 320 MPa UTS but with only 2–3% elongation, and 242.0-T77 retains useful strength at 250–300°C where 3xx.x alloys have already lost 40% of their room-temperature yield [S1]. For buyers building a sourcing checklist around these alloys, the aluminum extrusion profile selection guide covers the wrought side of the same EN 1780/AA family tree.
Standards, Designations and Traceability
Cast aluminum designations follow the Aluminum Association (AA) 3-digit system (with a .0 decimal marker for castings) on the American side and EN 1780 (formerly EN 1706) numerical-pattern codes such as 40000 for Al-Si, 20000 for Al-Cu, 50000 for Al-Mg, 70000 for Al-Zn, and 10000 for unalloyed [S1].
For procurement, the same heat must arrive with a mill certificate naming the AA designation, the EN 1780 numeric, the temper (F, O, T5, T6, T7, T77), and the chemical composition checked against the standard specification. The 242.0 cylinder-head reference table in standard metallurgy literature, for example, specifies Cu 3.5–4.5, Mg 1.2–1.8, Mn ≤0.35, Si ≤0.7, Fe ≤1.0, Ni 1.7–2.3, Ti ≤0.25, Cr ≤0.25, Zn ≤0.35, balance Al, and any deviation outside those windows puts the heat outside the 242.0 specification regardless of mechanical test results [S1]. Corrosion-critical castings additionally reference NACE MR0175 for sour-service H₂S environments and ASTM B26/B26M for sand-casting product form. Buyers should also confirm whether the foundry uses primary ingot, secondary returned scrap, or a blend, because the new-generation low-Fe (<0.2%) alloys effectively require primary feedstock [S1].
Process Capability and Common Defects by Family
Al-Si alloys (3xx.x) tolerate the widest range of section thickness, with eutectic or near-eutectic compositions flowing into features down to 2–3 mm wall in HPDC, while Al-Cu (2xx.x) alloys crack if the hot-spot modulus is not properly fed and demand hot-top risers or chills on any section above ~15 mm thickness [S1].
Common failure modes by alloy class: porosity dominates HPDC A380/383 castings, especially in sections thicker than 6 mm where the die-casting shot velocity window narrows; hot-tearing shows up in long, thin Al-Cu sand castings unless the foundry adjusts Si and Cu to reduce the freezing range; Fe-bearing intermetallics (β-AlFeSi needles) embrittle secondary-alloy 3xx.x castings, hence the <0.2% Fe ceiling on Aural-2/Silafont-36; and galvanic corrosion attacks any cast aluminum coupled to copper-alloy fasteners unless the joint is isolated with nylon washers or sealant. Foundries typically publish CT扫描 or radiographic-grade porosity acceptance criteria per ASTM E505 for HPDC safety parts, and the buyer should pre-agree sample-section locations on the part print before tooling release.
Application Shortlist by Industry
Use this condensed decision map as the starting shortlist: A380/A383 HPDC for non-structural and structural thin-wall housings; A356-T6 gravity casting for wheels, suspension links, and instrument housings; A319-T5 for engine blocks and transmission cases; 242.0-T77 for air-cooled cylinder heads above 200°C; 5xx.x Al-Mg (514.0, 535.0) for marine hardware and anodized architectural castings; 2xx.x (203.0, 204.0) for aerospace structural and military castings where strength and temperature outweigh cost [S1].
For the equipment-selection context around these castings, the hydraulic lift table capacity and duty-cycle guide and the gland packing vs O-ring pump sealing selection reference both touch on castings that sit in the same A356/A380 decision matrix (pump bodies, cylinder heads, valve bonnets). When the shortlist needs anodizing or architectural finish, the aluminum veneer panel specification reference covers the wrought sheet side while the same 5xx.x cast family handles the cast trim, mullions, and structural nodes.
Verify before PO release: mill certificate naming AA designation plus EN 1780 code, Fe content if the shortlist includes Aural-2/Silafont-36, temper code on the test report, and a written statement on primary vs secondary feedstock. Track on the next RFQ whether the foundry is quoting a 3xx.x baseline (A356/A380) or a low-Fe structural alloy, and confirm the heat-treatment furnace capacity if T6/T7/T77 temper is on the print.