Effects of carbon on the mechanical Properties & Microstructure of a Nb-based alloy

Sometimes materials need to be used very hot. This is true, for example, of materials in power generation (e.g.. a jet engine) where the efficiency of the process is proportional to the temperature. For a material to maintain its strength at high temperature it needs to have a high melting point. Such 'refractory' elements tend to be in the transition series in the periodic table. A good example of considerable current interest is niobium. Niobium is readily available and has a very highmelting point. It has two principal disadvantages, however. It oxidises, and therefore needs to be protected, and it loses its strength at high temperature. This project addresses the second of these problems.It has been found recently that reinforcing niobium with carbon not only improves the strength of the metal at high temperature, but, unlike most methods of strengthening niobium, does not make it brittle at low temperature.In the proposed work we will find out why and how carbides strengthen niobium, but do not make it brittle, and we will model both processes. We will then be able to optimise the level of carbon and the way in which the alloy is 'heat treated'.The future of this country's defence industry depends on its ability to understand and produce high temperature structural materials and thus stay competitive with other advanced manufacturing economies.