The magnesium alloy AZ91D is the most widely used magnesium die casting alloy, because of its excellent corrosion resistance, castability, and mechanical properties.

The AZ91D magnesium has a lower density compared to aluminum and zinc and meets the requirements for tensile strength, yield strength, and hardness.

But the magnesium alloy does not meet the thermal conductivity requirement.  And the alloy is much more expensive (even with the lower density) than the aluminum or zinc alloys.