Metastable structures in metallurgy

Abstract

Metastable structures or, more accurately, configurationally frozen metastable structures are no novelty in metallurgy. Indeed, much of the traditional practice of metallurgy has centered on the formation, characterization, understanding and control of structures which are either compositionally, topologically and/or morphologically metastable. However, in the past two to three decades we have seen a great upsurge in the production and study of new metastable structures in metallurgy, as well as in other condensed phase sciences. This upsurge reflects developments in the techniques of melt quenching, condensation and irradiation of materials, as well as in the kinetic understanding of structure evolution; and it has brought us nearer to making the concept of “ultramolecular engineering” viable. Among the new materials produced are glassy metals, highly super-saturated crystalline alloys and new alloys with exceptionally high interfacial densities. An overview of these new developments will be offered, following a discussion of the principles of metastable structure synthesis.