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Wednesday, May 17, 2006 - 9:00 AM
LAT063.1

Magnesium Alloy Elektron 21- a Light-Weight Solution up to 2000C (4000F)

P. Lyon, Magnesium Elektron, Manchester, United Kingdom

Magnesium alloys offer the opportunity to reduce weight due to their low density (2/3rds that of Aluminium). For this reason, Magnesium alloys are used in numerous aerospace applications including Helicopter transmissions and jet engine components.

Over the years, there has been a desire to improve the strength, temperature capabilities and corrosion performance of these alloys in line with the demands of ever onerous operating conditions. These objectives have been met by various alloys systems, most notably the Mg-Y-Nd-HRE-Zr alloy system, allowing operation at upto 2500C (4800F).

In more recent times, cost of components has become an increasingly important requirement. This has been addressed by the development of a new alloy from the Mg-Gd-Nd-Zr alloy system and is known as Elektron 21.This alloy maintains most of the property benefits of the Mg-Y-Nd-HRE-Zr alloy system (including corrosion performance, elevated temperature properties) however has been designed to have improved castability. A consequence of improved castability is reduced processing costs at the foundry. Interest by aerospace end users in this alloy has allowed the alloy to achieve AMS approval (AMS4429) and inclusion in the MMPDS design guideline. Consistency of properties is notable in both of these approvals.

The majority of work done with Elektron 21 has been for sand cast applications. Investment casting, is a means of reducing wall thickness (and hence weight) of complex components. This process is generally restricted to small components for Magnesium due to metal mould reaction. Use of low reactivity Elektron 21 gave successful results during investment casting (using plaster and shell moulds). Using improved processing technology, it has been shown that large components can be made successfully in this alloy with out reaction. This opens new opportunities for further weight reduction in weight sensitive applications.         


Summary: Magnesium alloys offer light weight opportunities, being only 2/3 the density of Aluminium. For users of speciality sand cast aerospace alloys, a number of Magnesium alloys are available. Some of the alloys offer adequate properties but suffer from poor corrosion resistance (Mg-Zn-RE-Zr), whilst others offer all of the advantages of good mechanical properties and corrosion resistance but require attention to foundry details and are more costly (Mg-Y-Nd-HRE). Elektron 21 is a Mg-Nd-Gd-Zr alloy designed to fulfil the needs of applications where a good package of castability, mechanical properties to 2000C/4000F and corrosion performance are required but at reduced processing cost. Strong interest from end users has allowed rapid achievement of AMS(4429) and MMPDS design approvals. Investment Castingof Aluminium alloys has offered a means of reducing component weight by achieving thin wall components. For Magnesium alloys, investment casting is comparatively limited due to metal mould reaction issues. It has been shown by foundry evaluations, that Elektron 21 is less prone to reaction than other elevated temperature Magnesium alloys. In addition development work has shown that, with correct processing conditions, large Elektron 21 castings can be produced without fear of metal mould reaction. This presentation focuses on advances made in alloy technology and touches upon complimentary investment casting technology. The outcome is a light weight solution which can operate at up to 2000C/4000F.