Magnesium Alloys - Metal Matrix Composites (MMC)

Background

Magnesium alloy metal matrix composite (MMC) products have been the subject of significant development activities. A range of alloy compositions have been used with particulate silicon carbide as the reinforcing phase. Major benefits of these materials are increased modulus, typically 40% higher than unreinforced magnesium alloys, and a specific gravity of only 2.0. The MMC also has good wear characteristics and a lower coefficient of thermal expansion than magnesium alloys. These properties have led to considerable interest from aerospace, automotive, bicycle and engineering industries.

The magnesium matrix wrought MMC product, Melram 072, has been developed in tube form and was launched around 1996. There is strong interest for cycle frame applications as thin wall Melram 072 tubes can be made 18% lighter than equivalent aluminium tube while retaining the required strength and stiffness.

Other wrought MMC products have also been developed in extruded form using various wrought magnesium alloys. The high stiffness/strength of these products should ensure they are attractive for a number of applications. A future development is to produce a cast magnesium MMC product and castings have already been made successfully using various techniques.

Key Properties

•         Light weight

•         Good stiffness to weight ratio

•         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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