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Cast Aluminum Alloys

Cast aluminum alloys use the three-digit Aluminum Association numbers (A380, A356, 413) and are formulated for the mold, not the mill: high silicon for fluidity and low shrinkage, copper for strength and machinability, magnesium so the alloy can be heat-treated after casting. They are chosen by casting process as much as by property — die casting needs the very fluid, non-heat-treated 3xx.x and 4xx.x grades; sand and investment casting can use the heat-treatable 356 and 357 family and reach forged-like strength in T6.

Popular cast aluminum grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityWeldabilityBest for
A3801593242.76Very goodPoorDie-cast housings, covers and brackets in volume
A3831503102.74Very goodPoorThin-wall die castings; better fill than A380
A3561652302.68GoodVery goodStructural sand and permanent-mold castings
A3572763452.67GoodVery goodHigher-strength aerospace castings
3561862622.67Very goodVery goodGeneral-purpose heat-treated castings
4131453002.66FairFairPressure-tight, thin-wall die castings
3191241862.79Very goodGoodEngine blocks and heads

All 184 cast aluminum grades

Choose cast aluminum for

Housings, brackets, pump and valve bodies, heat sinks, engine and gearbox parts in volume — anything with ribs, bosses and internal shapes that would be slow to machine from solid, once the quantity pays for the tooling.

Look elsewhere when

You need one to a few hundred pieces (machining from 6061 plate is cheaper than tooling), the part sees fatigue or impact loads (wrought alloys are tougher and porosity-free), or it must anodize to a uniform cosmetic finish — high-silicon castings anodize gray and blotchy.

Yield strength against elongation at break, Cast among every aluminum grade

No materials in view have both of these properties.

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Cast aluminum by application

Die-cast housings in volume
A380 is the default: fluid, pressure-tight, machinable, cheap. A383 (ADC12) for thin walls and complex fill; 413 when the casting must be leak-tight under pressure.
Structural castings
A356-T6 for wheels, suspension arms, pump bodies and anything load-bearing made by sand, permanent-mold or investment casting; A357-T6 where more strength is worth tighter process control.
Engine and thermal parts
319-T6 and 355 for blocks, heads and manifolds that run hot; A360 and 443 for corrosion-resistant marine fittings and cookware.
Prototype and low-volume parts
Machine from 6061-T651 or a cast tooling plate instead — no tooling, tighter tolerances, better surface. Move to casting when volume and geometry justify the mold.

Working with cast aluminum

Machining castings
Hard silicon particles abrade tools: use carbide or PCD, moderate speeds, and expect porosity to open up on machined faces (impregnate if it must seal). Datum from cast features and leave 1–2 mm machining stock on critical surfaces.
Heat treatment
Die-cast A380 / A383 / 413 are used as-cast (F) — trapped gas blisters if they are solution-treated. Sand and permanent-mold A356 / A357 / 319 are heat-treated to T5 or T6 for strength and dimensional stability.
Welding and repair
A356 and 356 weld and repair well with 4043 filler; A380 and other high-copper die castings weld poorly (porosity, cracking). Impregnation, not welding, fixes leaks in die castings.
Finishing
Powder coat, paint and chem-film are the usual finishes. Anodizing turns high-silicon alloys gray to black and uneven; A356 anodizes best of the group, A380 worst. Chromate or e-coat before paint for corrosion resistance.

Other aluminum series

Cast Aluminum Alloys — frequently asked

What is cast aluminum?

Cast aluminum alloys use the three-digit Aluminum Association numbers (A380, A356, 413) and are formulated for the mold, not the mill: high silicon for fluidity and low shrinkage, copper for strength and machinability, magnesium so the alloy can be heat-treated after casting. They are chosen by casting process as much as by property — die casting needs the very fluid, non-heat-treated 3xx.x and 4xx.x grades; sand and investment casting can use the heat-treatable 356 and 357 family and reach forged-like strength in T6.

Which grade of cast aluminum should I use?

A380 is the die-casting default for housings, brackets and covers in volume; A383 (ADC12 in Japan) is the same idea with slightly better fill for thin walls. A356-T6 for sand, permanent-mold and investment castings that carry load — wheels, suspension parts, pump bodies; A357-T6 where more strength is worth a tighter process. 413 for pressure-tight, thin-walled die castings; 319 for engine components. Cast plate for fixtures is its own series (tooling plate). For a prototype quantity, machining the part from 6061 is usually cheaper than tooling a casting.

Which grade of cast aluminum is the strongest?

AlMgSc has the highest yield strength in the series at 460 MPa; 201.0 follows at 420 MPa. Values are for each grade's default condition.

Which grade of cast aluminum is easiest to machine?

520.0 (machinability excellent, 90/100), then 850.0 (88/100).

Is cast aluminum heat-treatable?

Some grades are. Check the conditions listed on each grade page.

A380 or A356?

A380 is the die-casting alloy: fluid, cheap, pressure-tight, used as-cast for housings and covers in high volume. A356 is the sand and permanent-mold alloy: heat-treated to T6 it is stronger, tougher, weldable and anodizes better, used for structural castings like wheels and suspension parts. The process usually decides the alloy.

When should a part be cast instead of machined?

When the quantity pays for the mold — typically hundreds for sand casting, thousands for die casting — and the geometry has ribs, bosses and internal passages that a mill would spend hours on. Below that, machining from 6061 plate or a cast tooling plate is cheaper, faster and mechanically better.