Magnesium Alloys - Wrought Magnesium Alloys

Background

Magnesium alloys are used in wrought form including extruded bars, sections and tubes and also forgings and rolled sheet. Several wrought alloys are based on the Mg-Al-Zn system and are used in a range of engineering applications. ZW3 (Mg 3%Zn 0.6%Zr) was developed as a high strength extrusion and forging alloy and has been used in aerospace applications including forged aircraft wheels and gearbox housing parts for helicopters and aircraft. The highest strength wrought alloy is ZC71 and optimum properties are obtained in the T6 heat treated condition. Most wrought magnesium alloys are limited to operating temperatures of around 150°C. Thorium-containing wrought magnesium alloys have good high temperature properties but environmental problems associated with these alloys will preclude their future use. Yttrium-containing WE54/WE43 casting alloys were developed as high temperature wrought alloys which can be extruded or forged.

As wrought WE alloys have lower ambient temperature strengths than ZC71 and ZW3, they are less likely to be used in low temperature applications unless good corrosion resistance is also required. Most applications are likely to arise in high temperature parts where strength and creep are important. To date, most interest in wrought WE alloys has been for high temperature motor racing engine applications and several companies have forged WE54 engine parts. WE54 is being tested as a piston alloy due to its excellent high temperature properties compared to existing aluminium piston alloys. WE54 pistons are attractive because reduction in piston weight reduces inertial loads and increases power output. The aerospace industry also has interest in wrought WE alloys, particularly forgings, as a possible replacement for aluminium or other magnesium alloys.

Key Properties

•         Light weight

•         Low density (two thirds that of aluminium)

•         Good high temperature mechanical properties

•         Good to excellent corrosion resistance

Applications

Aerospace applications such as castings for gearboxes, transmissions, intermediate compressors, auxiliary gearboxes, generators, canopies and engine components.

Due to their light weight and mechanical properties they are used in motor racing applications to reduce vehicle weights.

Other applications include electronics, sporting goods, nuclear applications, office equipment, flares, sacrificial anodes, flash photography and tools.

Primary author: L. Duffy

Source: Materials World, vol. 4, pp. 127-30, 1996

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