AZ91D Magnesium (Die Cast) vs A380
AZ91D and A380 are the workhorse alloys of their families: AZ91D is the most widely used magnesium die-casting alloy, and A380 is the most common aluminum die-casting alloy. The core trade is weight versus strength and cost. AZ91D is dramatically lighter, while A380 is stronger, handles higher temperatures, casts more forgivingly, and costs less, making it the volume default for housings.
The verdict
Choose A380 for the broadest range of high-volume die-cast housings where strength, higher temperature tolerance, easier casting, and lowest cost matter. Choose AZ91D when shaving mass is the goal: at 1.81 g/cc it is roughly one-third lighter than A380 (2.71 g/cc), ideal for handheld and portable thin-wall enclosures.
Side-by-side data
| Property | AZ91D Magnesium (Die Cast) | A380 |
|---|---|---|
| Category | Magnesium | Aluminum |
| Density (g/cm³) | 1.81 | 2.71 |
| Tensile strength (MPa) | 230 | 324 |
| Yield strength (MPa) | 150 | 159 |
| Elongation (%) | 3 | 3 |
| Hardness | 63 HB | 80 HB |
| Max service temp (°C) | 120 | 170 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 72 | 96 |
| Typically used for | Thin-wall lightweight housings | High-volume die-cast housings |
Which should you choose?
Choose AZ91D Magnesium when…
- Minimum weight drives the design: 1.81 g/cc is about 33% lighter than A380 aluminum
- Casting thin-wall, intricate handheld or portable housings (tools, electronics, cameras)
- Excellent castability and dimensional detail in thin sections are needed
- Vibration damping and EMI shielding of a magnesium enclosure add value
- Machinability is a plus: AZ91D rates 5/5, the top of the scale
- Service stays cool: AZ91D is limited to roughly 120 C max
Choose A380 Aluminum when…
- You want the lowest cost: A380 rates 1.8/5 vs AZ91D's 3.0/5
- Higher strength matters: 324 MPa tensile vs AZ91D's 230 MPa
- Service runs warmer: A380 tolerates ~170 C vs ~120 C for AZ91D
- Producing the broadest range of general-purpose die-cast housings at volume
- Better corrosion resistance is needed (A380 3.0/5 vs AZ91D 2.5/5)
- You want a forgiving, well-understood alloy with wide foundry availability
Key differences that matter
- Weight is AZ91D's headline advantage: at 1.81 g/cc it is roughly one-third lighter than A380 (2.71 g/cc).
- A380 is stronger in tension (324 vs 230 MPa) and higher in yield (159 vs 150 MPa nominal).
- A380 is the cheaper alloy (cost 1.8/5 vs 3.0/5), reinforcing its role as the volume die-cast default.
- A380 tolerates higher temperature (~170 C vs ~120 C), so magnesium is restricted to cooler-running parts.
- Both are die-casting alloys with low elongation (3%), so neither is suited to ductile, high-deflection parts.
- Magnesium requires controlled handling: fine chips and dust are flammable, a foundry and machining consideration.
- A380 edges corrosion resistance (3.0 vs 2.5); magnesium castings usually need coating or sealing for service.
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Open the Material SelectorGet a Quote →Frequently asked questions
How much lighter is AZ91D magnesium than A380 aluminum?
AZ91D has a density of about 1.81 g/cc versus 2.71 g/cc for A380, so a magnesium casting is roughly one-third lighter than the same part in aluminum. That weight reduction is the main reason AZ91D is chosen for handheld and portable enclosures despite its higher cost.
Why is A380 the more common die-casting alloy?
A380 combines good strength, easy castability, higher temperature tolerance, and the lowest cost in this pairing (1.8/5). It casts well into a huge range of housings and brackets, has wide foundry availability, and is forgiving in production, which makes it the default high-volume aluminum die-cast alloy.
Is magnesium die casting more expensive than aluminum?
Yes. In our data AZ91D rates 3.0/5 on cost versus 1.8/5 for A380, so the magnesium alloy is meaningfully pricier. The premium buys roughly one-third weight savings, so magnesium is justified mainly when reducing mass delivers clear product value.
Can AZ91D run as hot as A380?
No. AZ91D is limited to about 120 C, while A380 tolerates roughly 170 C. For parts near heat sources or in warm enclosures, aluminum holds properties better. Magnesium should be reserved for cooler-running applications where its weight advantage is the priority.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.