Die Casting Materials

Die Casting materials

Pictures	Materials		Details
	Aluminum Alloys	ADC12	Our aluminum alloy. With good strength-to-weight ratio, excellent machinability and natural corrosion resistance.
		A380	The aerospace-grade material with excellent strength-to-weight ratio and high strength and hardness.
		A356	The strain hardening aluminum alloy with excellent corrosion resistance. Suitable for marine applications. Can be welded.
	Zinc Alloys	Zamak 3	The most common stainless steel. It is non-magnetic steel.
		Zamak 5	SS316 has superior corrosion resistance in chloride containing environments, with good elevated temperature strength.
		ZL0410	SS303 has excellent toughness, but lower corrosion resistance than 304
		ZL0430	SS430 is a non-hardenable steel containing straight chromium, and belongs to the ferritic group of steels.

Aluminium, Zinc and Magnesium: The Three Die Casting Families

Almost every die-cast part falls into one of three alloy families. Each has a different balance of strength, weight, corrosion resistance and cost.

Aluminium alloys — the most common choice. Good strength-to-weight ratio, excellent castability, takes almost any finish. Used for housings, brackets, heat sinks and structural covers.
Zinc alloys — denser but extremely castable. Very thin walls, sharp detail and tight tolerances come easily; ideal for small precision parts and decorative hardware.
Magnesium alloys — the lightest option, used where every gram counts. More reactive and costlier to process, so reserved for weight-critical applications.

Alloy Selection Guide

Alloy	Family	Key properties	Typical use
ADC12	Aluminium	Excellent fluidity, good strength, easy to cast	General housings, covers, brackets
A380	Aluminium	Balanced strength and castability, widely available	Electronics enclosures, automotive parts
A356	Aluminium	Higher strength and ductility, heat-treatable	Structural and pressure-tight parts
Zamak 3	Zinc	Very thin walls, tight tolerance, easy plating	Small precision and decorative parts
AZ91D	Magnesium	Lightest, good strength-to-weight	Weight-critical housings

The table above lists what we cast most often. Where a drawing calls for a specific grade, we work to that specification rather than substituting a convenient alloy.

Porosity and How to Control It

Porosity — internal gas or shrinkage voids — is the defining quality issue in die casting. It affects pressure tightness, machined surface appearance and fatigue life. It cannot be eliminated entirely, but it can be managed:

Good casting design. Uniform walls, generous radii and correct draft let metal fill and cool evenly.
Controlled fill. Gate and runner design, plus vacuum assistance on demanding parts, reduce trapped gas.
Thermal management. Die cooling channels and cycle timing control shrinkage porosity.
Process discipline. Stable shot parameters and die temperature keep results repeatable batch to batch.
Machining allowance. A small machining stock lets us cut below the porous skin on sealing faces.

Die Casting vs CNC Machining

The two processes are usually partners rather than rivals. Die casting produces a near-net shape cheaply at volume; CNC machining then cuts the critical faces, bores and threads to tolerance. The standard workflow is cast, then machine — the casting removes most of the material cost and the machining delivers the precision.

For low volumes, machining from solid is often the better choice because it avoids tooling. The crossover is driven by volume, part size and the amount of finish machining required.

Frequently Asked Questions

Is a die-cast part as strong as a machined one?

Generally no — cast alloys are less ductile than their wrought equivalents. Where peak strength is needed, a machined wrought part is better; where complex near-net geometry at volume matters, casting wins.

Can die-cast parts be anodised?

They can, but cast aluminium takes anodising less evenly than wrought material because of its silicon content and porosity. Powder coating and painting give more consistent results on castings.

What volumes justify a die?

Die casting becomes economical once tooling cost is spread over volume; below that threshold, machining or sand casting is usually the sensible route.

How tight a tolerance can a casting hold?

A general casting tolerance is measured in fractions of a millimetre. Tight tolerances are achieved by machining the critical features after casting, not by the casting process itself.

Die Casting Materials