Volume 5, Issue 3, August 2015

Special issue on superplasticity
Guest editors: Terence G. Langdon, Megumi Kawasaki, Roberto B. Figueiredo

Preface

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Superplasticity refers to the exceptionally high elongations which may be achieved in some polycrystalline materials when pulling in tension. Although this phenomenon was identified and examined experimentally more than seventy years ago, it was initially considered little more than a scientific curiosity. Later, it became clear that the easy and relatively inexpensive forming of curved and complex shapes was highly beneficial in a wide range of applications, covering such diverse areas as aerospace to automotive, and accordingly the processing operation was extensively developed to form the basis for the worldwide superplastic forming industry. The consequent interest in superplastic forming led to the initiation of many investigations of the superplastic effect at institutions around the world and it led also most notably, thirty years ago in 1985, to the founding of the Institute of Metals Superplasticity Problems of the Russian Academy of Sciences in the city of Ufa in the Urals region of Russia. This was the first, and remains the only, institute devoted exclusively to research on all aspects of superplasticity in a very wide range of materials.
Achieving superplastic flow is not easy. It requires both a very small grain size, typically smaller than ~10 µm, and a high operating temperature, typically at or above about one-half of the absolute melting temperature of the material. The requirement of a very small grain size was initially achieved through the use of thermo-mechanical treatments but in 1988, in a classic report published in the earliest days of the institute, it was demonstrated that it may be possible to achieve submicrometer or even nanometer grain sizes through the application of severe plastic deformation (SPD). This is now known as SPD processing and it has become a major research topic at many universities and materials science institutes around the world. It is appropriate, therefore, to bring together recent reports which serve to describe some of the new developments in this important field and to publish these papers in a journal having editorial offices in Ufa.
As guest editors of this special edition of Letters on Materials devoted exclusively to superplasticity in materials processed by SPD techniques, we would like to express our warm thanks to the numerous authors who responded enthusiastically to our requests for papers for this special issue. Their cooperation, and especially their promptness in meeting deadlines, made our task extremely easy. Finally, we should mention that all of the papers in this volume were invited but nevertheless they were reviewed to the high standards always required for good quality scientific publications.