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CONCERTED EUROPEAN ACTION ON STRUCTURAL INTERMETALLICS

Objectif


The work on TiAl-based alloys has allowed a broadly-based study of the processing, structure and properties of a specific alloy, Ti-48Al-2Mn-2Nb to be carried out, together with a range of studies on closely related alloys. Secondary processing of these alloys has shown that isothermal forging can be successfully carried out and that there are advantages for certain applications to using high temperature extrusion, rather than forging. Joining experiments on these alloys has defined the optimum approach. Property and micro-structural studies have resulted in clear correlations between the very different structures which can be generated in these alloys and the properties. The very extensive primary creep found in the base alloy has been shown to be greatly reduced with suitable alloying additions. Alloy development, carried out in a number of partners' laboratories, has resulted in proprietary alloys being developed, which have properties which are significantly better than the CEASI base alloy. Fundamental studies have focussed on the complex structures observed in rapidly cooled samples and the complex nature of crystal defects and interfaces in these alloys.

The work on iron aluminides concentrated on a dispersion-hardened FeAl40 alloy. Target properties, defined by industrialists were aimed at using a range of process routes, (casting, gas atomisation, mechanical alloying, extrusion, rolling). Variations in alloying additions were made and the influence on structure and properties of the alloys investigated. The conclusion from the work is that the alloys investigated are very close to industrialisation but further work is needed and a production route that results in an affordable alloy must be developed. Perhaps the nearest area of application is in the use of these highly corrosion-resistant alloys as coatings on less expensive but less corrosion-resistant alloys.

The work on a NiAl-based alloy was less successful because a major problem in processing this alloy was found which could not be overcome. Ingot material was melted and atomisation was carried out, but subsequent mechanical alloying was unsuccessful. This unexpected limitation could probably have been overcome if facilities had been available for milling the powder at liquid nitrogen temperatures, but no such facility was available within the consortium. Once this conclusion had been reached further work aimed at producing suitable material for the envisaged application was discontinued, although some limited work on the powder was completed.

An assessment of the European effort in the area of more exotic intermetallics (e.g. silicides, niobium aluminides) has been made as part of the CEASI programme and it was concluded that at present there is little chance of a coherent programme being developed.
The world-wide activity on intermetallics is assessed and it is concluded that there is the need for a European concerted action. There is very strong support for this within industry, in universities and in research insitutes. At present European work is highly fragmented and almost exclusively concerned with scientific rather than engineering objectives. To counter the increasing threat from other parts of the world the intermetallic-based research in Europe should be coordinated and steered towards undustrial targets.

In order for there to be a useful concerted action it has become apparent that there is the need for a supply of clean-melted, well-characterised material, in quantities which will allow many different laboratories to carry out their research programme. Recent work has demonstrated that such material can now be produced in Europe, by a number of routes with potential commercial viability, and this fact is important in the overall timeliness of this proposal.

The potential market for intermetallics is estimated to be at least 100MECU over the next ten years and this concerted action is aimed at increasing Europe's share of this world-wide market.

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UNIVERSITY OF BIRMINGHAM
Contribution de l’UE
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Adresse
EDGBASTON
B15 2TT BIRMINGHAM
Royaume-Uni

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