Magnesium alloy is one of the most preferred material used in DSLR Bodies, Laptops and other Gadgets. It is a mixture of Magnesium and alloy which is often aluminum, zinc, copper, silicon, zirconium and other minerals, and to answer your question why not aluminum? Well, not only aluminum but a combination of the said minerals. This mineral is also used in aerospace and automotive industries.
It is preferred by manufacturers because:
- It is the lightest structural metal which makes it ideal for gadgets of everyday use. It's lightness is one of its key property. Weight reduction is one of its advantages. Aluminum is twice heavier while Steel is five times heavier than of the Magnesium alloy.
- It is easily machined, cast, forged and welded.
- It has good to excellent corrosion resistance. Corrosion is the gradual destruction of materials usually metals by chemical reaction, which comes from its environment. As we know that DLSRs usually exposes to these chemical reactions which makes Magnesium alloy a very good choice for its body.
- Magnesium is the eighth most common element on earth's crust and fourth most common element on earth as a whole. It's abundance means more productivity and because of its availability, manufacturers can produce cheaper gadgets. Not to mention that it is also recyclable.
- Although not a big issue for cameras, but it has a good high temperature mechanical properties. It is a common choice for high temperature applications like automotive.
- About its densities, it is stronger than plastics, and even strong enough for cameras bodies.
All these stuffs makes Magnesium Alloy a promising material.
Here are some tests that was done on a Magnesium-made Tripod.