The role of energy in the modern world goes beyond mere technology and economics to influence welfare, environment, life quality and, broadly, civilisation. Since the industrial revolution, energy conversion technology has been at the forefront of innovation required to satisfy the needs of mankind. This technology more than others has always been very dependent on the performance of the materials used; especially over the last two decades during which efficiency and environmental concerns have become challenging objectives. In this context the European Commission has developed significant collaborative programmes in Europe within the COST framework, to enhance the state of the art in this technology. The Li~ge Conferences pursue the mission to report on the achievements of these programmes in the light of progress made elsewhere. The first four conferences in this series were held in 1978, 1982, 1986 and 1990, and provided the opportunity to present and review the work of the EuropeanMaterials Collaborative Programmes COST-50 (gas turbines), COST-505 (steam turbines) and COST- 501 (energy conversion from fossil fuels). The proceedings of these conferences were published by Applied Science Publishers (1978) and by D. ReideIlKluwer Publishing Company (1982, 1986 and 1990). While the first two Conferences have dealt essentially with high temperature alloys for gas turbines (COST 50), the third and fourth Conferences held in 1986 and 1990 were concerned with a broader range of topics, including the work of the third round of COST-50 (1972-1983), that of COST-50l, which was initiated in 1981 and COST 505 (1983-1990).