MG · magnesium
Magnesium Alloy AZ91E (sand cast, high purity)
The sand-casting version of AZ91 with a high-purity specification: lower strength than the die-cast grade but a far lower casting cost for low volumes, and it machines the same way.
Quoting this material
- Typical lead time
- 20–35 working days
- Condition
- As sand cast, T6 option (solution treated and aged)
- Achievable finish
- Ra 3.2 µm (as cast) typical · Ra 0.8 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
The sand-casting version of AZ91 with a high-purity specification: lower strength than the die-cast grade but a far lower casting cost for low volumes, and it machines the same way.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 165–275 | MPa |
| Yield strength (0.2%) | 97–165 | MPa |
| Elongation | 2–6 | % |
| Hardness | 65–75 | HB |
| Thermal conductivity | 51 | W/m·K |
| Modulus of elasticity | 45 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
As sand cast, T6 option (solution treated and aged)
Heat treatment
Can be solution treated and aged (T6) to raise the strength, which is not available on the die-cast grades - a casting that has porosity cannot be solution treated without blistering.
Achievable surface finish
Ra 3.2 µm (as cast)
Ra 0.8 µm
Sand castings have a rougher skin than die castings, so more stock has to be removed to reach a machined surface.
Tooling and cutting parameters
Cutting speed
- 300–700 m/min (sharp uncoated carbide)
Feed
- 0.10–0.35 mm/rev turning · 0.10–0.30 mm/tooth milling
Tooling
- Sharp uncoated carbide with large clearance
Coolant
- Mineral-oil mist or dry
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Aerospace castings at moderate volumes
- Low-volume instrument housings
- Prototype magnesium castings
- Defence equipment castings
- Commercial equipment housings
DFM notes for this grade
- Sand casting is the route to a magnesium part at low volume: no tooling cost, and the T6 option is available where the strength is needed
- The E specification is the high-purity one: for magnesium, the corrosion performance depends on it, and the older non-purity grades corrode far faster
- Machining allowance on a sand casting is larger than a die casting - the surface finish and dimensional tolerance of a sand casting are both looser
Questions buyers ask
- When is a sand cast magnesium part the right answer?
- Low volume or a complex shape that a die cannot justify. A sand casting has no tooling cost, so for a handful of parts or a large aerospace casting it is the only economic route; the trade is a rougher surface and more machining stock.
- Why can the sand casting be heat treated when the die casting cannot?
- Porosity. Solution treatment requires a high temperature hold, and gas trapped in a die-cast part expands and blisters the surface. A sand casting has much less trapped gas, so the T6 treatment can be applied.
Grades we would quote instead
AZ91D
8/10The most common die-casting magnesium: high aluminium content gives good castability and decent strength, and it machines fast with excellent finishes.
AM60B
8/10The ductile die-casting magnesium: less aluminium than AZ91, so lower strength but far better elongation.
AZ31B
9/10Magnesium machines faster than aluminium with a sharper finish, provided the chip is kept moving and the swarf rules are respected.