Aluminum Casting Alloys - Complete Selection Guide

Aluminum casting alloys look like an alphabet soup - A380, A356, ADC12, 319, 535 - but the logic is simple once you sort them by process and by what the alloying elements do. This guide organizes the whole family so you can shortlist in five minutes.

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The Numbering System in 30 Seconds

Cast aluminum alloys use a three-digit series (xxx.x):

Series	Main alloying element	Character
2xx	Copper	High strength, poor castability/corrosion
3xx	Silicon (+Cu, Mg)	The casting mainstream - best fluidity
4xx	Silicon (high)	Wear resistance, special uses
5xx	Magnesium	Corrosion resistance, anodizing, marine
7xx	Zinc	High strength, sand casting specialty
A356-class	Si 7% + Mg	Structural standard

An "A" prefix (A380, A356) denotes the modified/premium composition version of the base alloy.

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The HPDC Workhorses (3xx Series)

These carry 0.8-1.3% iron to protect dies - the defining HPDC trait. Used as-cast (no T6).

Alloy	Si	Cu	Tensile	Best for
A380	7.5-9.5%	3-4%	320 MPa	The global default - 80% of aluminum die castings
ADC12	9.6-12%	1.5-3.5%	310 MPa	JIS standard, A383's twin, Asia supply chain
A383	9.5-11.5%	2-3%	310 MPa	Thin walls, dense fins, leak-tight parts
A360	9-10%	0.6%	300 MPa	Corrosion resistance over castability
A413	11-13%	1%	290 MPa	Pressure-tight hydraulic parts
A390	16-18%	4-5%	280 MPa	Wear surfaces, cylinder liners

The Structural Alloys (Gravity / LPDC / Sand)

These are low-iron, heat-treatable alloys - a different world from HPDC:

• A356 (Si 7%, Mg 0.3%): the structural standard. T6 delivers roughly 262-270 MPa with 3-8% elongation. Wheels, chassis, aerospace brackets
• A357: adds beryllium for premium aerospace strength
• 319: Si 6%, Cu 3.5% - general sand/gravity engineering alloy, good machinability

The Specialty Series

• 5xx (535, 518): magnesium-rich - the best corrosion resistance and anodizing response of cast aluminum; marine hardware and decorative parts. Difficult to cast
• 7xx (713): zinc-bearing, age-strengthening without full T6 - furniture and sand-cast structural parts
• 2xx (206, 242): copper-rich, high-temperature strength (pistons), but poor castability and corrosion resistance

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Selection by Application

Your requirement	Alloy shortlist
Standard housings at volume	A380 / ADC12
Thin walls under 1.5 mm, fins	A383
Leak-tight hydraulic/pneumatic	A413, A383
Structural + T6 + weldable	A356 (gravity/LPDC, not HPDC)
Marine / outdoor corrosion	A360 or 535
Decorative anodized finish	535 (not high-Si HPDC alloys)
Wear surfaces	A390
High-temperature (over 150°C)	242, or reconsider zinc ZA-27 under 150°C

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The Questions Buyers Ask Most

Can I get A356 properties in die casting?

Not fully. Standard HPDC A356 suffers die soldering (low iron) and cannot T6 (gas porosity). The honest options: vacuum die casting with structural alloys, or switch process to gravity/LPDC. See A356 vs A380 for the full trade-off.

A380 vs ADC12 - does the choice matter?

Functionally they are near-twins (ADC12 vs A380). ADC12's wider composition window makes it the pragmatic choice for Asia-sourced programs; drawings often specify "A380 or ADC12."

Why do HPDC alloys contain iron?

Iron (0.8-1.3%) prevents the molten aluminum from soldering to the steel die. It costs some ductility - which is exactly the trade structural alloys like A356 refuse to make.

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Related Guides

• die casting materials - the full materials hub (zinc, magnesium too)
• aluminum for die casting - buyer-focused alloy selection
• aluminum vs zinc die casting - metal family decision
• aluminum casting - the process landscape

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