Magnalium
Magnalium is a class of aluminium-magnesium alloys, with a variety of uses from machine parts to pyrotechnics, depending on the Al-Mg ratio.
Contents
Composition
Magnalium consists of aluminium and magnesium in different ratio. The common alloy used for bulk materials consists of 95% Al and 5% Mg by weight. The alloy used in pyrotechnic mixtures consists of 50% Al and 50% Mg, which is why this alloy is sometimes wrote as AlMg 50:50.
Properties
Magnalium alloys containing ~5% magnesium exhibit greater strength, greater corrosion resistance and lower density than pure aluminium, making them more workable and easier to weld than pure aluminium. Alloys containing higher percentage of magnesium (5-50%) are much more brittle and will corrode much easier, due to higher magnesium content. The melting point for AlMg 50:50 is 435 °C.
The chemical reactivity of magnalium depends on the Al-Mg ratio: Al-rich magnalium alloys will be corroded by both strong acids and bases, while Mg-rich magnalium alloys are more susceptible to most acids, as well as water. The latter is also much more flammable. Neither types resist halogens.
Availability
Bulk magnalium is available as machine parts, and can be bought from stores and suppliers.
Powdered magnalium can be bought from chemical and pyrotechnic suppliers. Although not officially restricted, magnalium powder may be regulated in the EU, as the directive restricting explosive precursors regulates any substance or mixture of magnesium or aluminium powder containing 70 % w/w or more of aluminium or magnesium.[1]
Preparation
Magnalium can be prepared by melting aluminium and magnesium in their desired ratios. To turn the bulk metal into a powder, a ball mill is commonly used.
Projects
- Flash powder
- Reducing agent
Handling
Safety
Magnalium is flammable and if ignited will burn with a blinding bright white flame. Magnalium flames, like all magnesium flames cannot be extinguished by water, and a class D fire extinguisher should be used. In you don't have one, powdered magnesium oxide can be used to put out the magnesium fire.
Storage
In closed airtight bottles, away from moisture, acids and fire.
Disposal
Can be neutralized by burning it into a kiln or neutralized by using an acid that dissolves both magnesium and aluminium, like hydrochloric acid. Use dilute acid and add only small amounts at a time.
