Alloy AZ91D is the most widely specified magnesium die casting alloy. This high-purity alloy has an excellent combination of mechanical properties, corrosion resistance, and castability.
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Alloy AZ91D is the most widely specified magnesium die casting alloy. This high-purity alloy has an excellent combination of mechanical properties, corrosion resistance, and castability.

Corrosion resistance is achieved through the enforcement of very strict limits on three metallic impurities: iron, copper and nickel. These are limited to very low levels making it necessary to use primary magnesium in the production of this alloy. As with all magnesium alloys, special precautions must be taken when machining.

Effects of Temperature, Time and Environment on Mechanical Properties of Magnesium alloys: Designers of structural components should be aware of the creep limitations of magnesium alloys. Die castings are required to operate under a variety of conditions that can affect the mechanical properties. In general, with increasing temperature, the tensile strength, yield strength and hardness of magnesium alloys decrease, while ductility increases. The links below give typical stress-strain curves over the temperature range from -50°C to 200°C.

It is important that when designers are selecting the appropriate magnesium alloy for a particular environment that all of the factors are considered. In addition to environmental effects, there is a change in the metallurgical structure of the alloy over a period of time, and/or at elevated temperatures, that affects the mechanical properties. This aging effect arises from the fact that the castings are produced under rapid solidification conditions that do not allow the alloy to reach equilibrium (effectively, reactions between the alloy constituents have not been completed).

The best alloy for a particular elevated temperature application cannot be selected on the basis of short-time strength at normal operating conditions. Because creep is an important consideration in magnesium parts for elevated temperature use, stresses and times of operations should be known for both peak and normal conditions. Thus, the limits of stress, time, and allowable deformation during operation at given temperature determine the best alloy for each application.

This alloy exhibits excellent damping capacity and vibration attenuation in comparison with aluminum die casting alloys.