Residuals and properties

Abstract

The awareness of purity in materials in relation to properties is historically of long standing. Today, this awareness has been heightened both because of a better understanding and also because of the realization of the economic benefit in improved performance, especially in complex metallurgical structures. A further stimulus to the growing interest in this field has been a serious concern with an inevitable accumulation of unwanted impurities arising from increasing effort in materials recycling. By good fortune, the timely arrival of instrumental and other technical developments has opened up new opportunities for detailed investigations. This introductory paper takes a synoptic view of the subject and in particular considers the common links underlying behaviour in a range of phenomena represented at the meeting. In terms of mechanisms, the main interconnecting thread lies in the capacity of dilute impurities to concentrate at various interfacial localities by equilibrium or kinetic processes. This may induce subsidiary effects, such as reduced cohesion or retarded surface reactivity. We are at a point when positive action can be taken to translate the new data into materials practice, both by tightening specifications in bulk impurity contents and also by introducing process remedies based on physicochemical treatments.