These compounds are flammable when powdered, are more resistant to corrosion than pure magnesium, and are generally more reactive than pure aluminium; they are used in pyrotechnics as a metal fuel for colored flames, to produce sparks in some glitter and streamer stars, and as a more consistent replacement for separate magnesium and aluminum powders in crackling microstars (dragon eggs).
[2]: 57 In some cases the normally faster-reacting magnesium component of magnalium serves to slow down a reaction due to its higher reactivity in a composition.
This occurs in dragon eggs, where slower oxidation of magnesium by Lead tetraoxide (Pb3O4) allows time for the formed Lead monoxide (PbO) gas to build up without reacting with the aluminum portion, so when the magnesium is finally consumed the aluminum reaction occurs rapidly enough to produce an explosion.
If too much magnesium is present in the alloy (or added to the mix), it will burn continuously but not produce the desired effect.
Similarly too little magnesium will prevent enough PbO vapor from building up to react rapidly and the aluminum will simply burn.