AZ91C is a magnesium alloy used primarily for casting. Containing 8.7% aluminum (relatively high for the AZ family of magnesium alloys) and 0.7% zinc, it provides a combination of ductility, toughness, and low mass that’s attractive for a wide range of applications. As with other AZ alloys, AZ91C magnesium is readily machinable and has a high strength-to-weight ratio. It’s also nonmagnetic, has good vibration damping properties, as well as good electrical and thermal conductivity.
The alloy’s corrosion resistance is generally good, but it is susceptible to attack by chloride solutions, limiting its use where salt exposure is likely, although surface treatments and T6 heat treatment can reduce this issue.
AZ91C is widely used in automotive and aerospace applications where low mass is a higher priority than high strength, in consumer electronics, and for RFI and EMI shielding.
In sand casting and die-casting applications, AZ91C pours and flows well, and can produce thin sections. It also has low shrinkage, which helps avoid internal defects and improves dimensional stability.
Caution is needed when using AZ91C as it can be flammable in fine powder form. Additionally, we do not recommend this alloy for applications with sustained temperatures above 300°F as it can suffer from creep. Welding can be difficult, with TIG welding being preferred over MIG. Best results are achieved using Friction Stir Welding.
| Property | Value | Notes |
|---|---|---|
| Material Type | Magnesium-aluminum-zinc alloy | UNS M11914 |
| Density | 1.81 g/cm3 | 0.065 lb/in3 |
| Melting Point | ~ 470-600°C | ~ 879-1,100°F |
| Hardness (Brinell) | 55-70 | Highest in T6 temper |
| Tensile Strength | ~ 170-270 MPa | ~ 24,000-39,000 psi |
| Yield Strength | ~ 83-130 MPa | ~ 12,000-19,000 psi |
| Elongation at Break | ~ 2.3-15% | Highest in T4 temper |
| Modulus of Elasticity | ~ 46 GPa | ~ 6.7x106 psi |
| Corrosion Resistance | Good overall but vulnerable to chloride solutions | T6 temper increases resistance, anodizing is widely used |
| Magnetism | No | |
| Heat Treatment | Available in T4 and T6 tempers | |
| Machinability | Good | |
| Weldability | Moderate | TIG preferred over MIG, Friction Stir Welding yields best results. |
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