Table of contents

An introductory review of various concepts about first-order phase transitions is given. Rules for classification of phase transitions as second or first order are discussed, as well as exceptions to these rules. Attention is drawn to the rounding of first-order transitions due to finite-size or quenched impurities. Computational methods to calculate phase diagrams for simple model Hamiltonians are also described. Particular emphasis is laid on metastable states near first-order phase transitions, on the 'stability limits' of such states (e.g. the 'spinodal curve' of the gas-liquid transition) and on the dynamic mechanisms by which metastable states decay (nucleation and growth of droplets of a new phase, etc.).

Some of the main principles which determine the protective nature of oxide scales on metals in oxidising environments at high temperature are considered and discussed with particular respect to NiO scales on nickel and Cr₂O₃ and Al₂O₃ scales on high-temperature alloys. Emphasis is given to the transport processes in the scales and the importance of short-circuit diffusion paths. The development of stresses during oxidation are discussed and related to the effectiveness of the scales in resisting mechanical breakdown. Relief of these stresses can occur by deformation of the oxide or metal substrate but, in certain circumstances, may result in fracture and/or loss of adhesion of the scale followed by spalling from the metal surface, sometimes with catastrophic consequences.