Magnesium Alloy

Magnesium Alloy

Magnesium alloys are mixtures of magnesium with other metals (called an alloy), often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminum, copper and steel. Therefore magnesium alloys are typically used as cast alloys, but research of wrought alloys has been more extensive since 2003. Cast magnesium alloys are used for many components of modern cars, and magnesium block engines have been used in some high-performance vehicles; die-cast magnesium is also used for camera bodies and components in lenses.

Practically all the commercial magnesium alloys manufactured in the United States contain aluminum (3 to 13 per cent) and manganese (0.1 to 0.4 per cent). Many also contain zinc (0.5 to 3 per cent) and some are hardenable by heat treatment. All the alloys may be used for more than one product form, but alloys AZ63 and AZ92 are most used for sand castings, AZ91 for die castings, and AZ92 for most used for permanent mold castings (AZ63 and A10 are sometimes used). For forgings, AZ61 is most used, with M1 employed where low strength is required and AZ80 for highest strength. For extrusions, a wide range of shapes, bars, and tubes is made from M1 alloy where it’s low strength suffices or where welding to M1 castings is planned. Alloys AZ31, AZ61, and AZ80 are employed for extrusions in the order named, where their increase in strength justifies their increased cost.

Magnox (alloy), whose name is an abbreviation for 'magnesium non-oxidising', is 99% magnesium and 1% aluminium, and used in the cladding of fuel rods in some nuclear power stations.

Magnesium alloys are referred to by short codes (defined in ASTM 275) that denote the approximate chemical composition by weight. For example, AS41 has 4% aluminium and 1% silicon; AZ81 is 7.5% aluminium and 0.7% zinc. If aluminium is present, manganese is almost always also there at about 0.2% by weight to improve grain structure; if aluminium and manganese are absent, zirconium is usually present at about 0.8% for the same purpose.