Magnalium is an aluminium alloy with 1.5 to 2% magnesium and small amounts of copper, nickel, and tin. Some alloys, intended for particular uses at the cost of poor corrosion resistance, may consist of up to 50% magnesium. It finds use in engineering and pyrotechnics.
Alloys with smaller amounts of magnesium (about 5%) exhibit greater strength, greater corrosion resistance, and lower density than pure aluminium. Such alloys are also more workable and easier to weld than pure aluminium. Alloys with high amounts of magnesium (around 50%) are brittle and more susceptible to corrosion than aluminium.
Although they are generally more expensive than aluminium, the high strength, low density, and greater workability of alloys with low amounts of magnesium leads to their use in aircraft and automobile parts. Alloys with about 50% magnesium are brittle and corrode easily, which makes them unsuitable for most engineering uses. However, these alloys are flammable when powdered, are more resistant to corrosion than pure magnesium, and are more reactive than pure aluminium and are therefore used in pyrotechnics as a metal fuel and to produce sparks. Magnalium powder also burns with a crackling sound if burnt by itself, and provides a good compromise between the reactivity of magnesium, and the stability of aluminium. Another benefit for pyrotechnics is the brittleness of the alloy, as mentioned before. It is easily broken with a hammer and then ground in a coffee grinder to usable powder. It will grind in a ball mill into a fine powder in a matter of hours, as opposed to a matter of days with aluminium powder.
Although it is much more powerful than aluminium powder (when compared at similar mesh size) and similar precautions should be taken as per magnesium. These include dangers of moisture and incompatibility with other compounds (boric acid and ammonium compounds).
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