New discoveries in deformed metals

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New Discoveries in Deformed Metals

NIELS HANSEN ROBERT F. MEHL AWARD MEDALIST

Microstructural analysis by advanced and automated methods has allowed deformation microstructures to be quantified in terms of common structural parameters. This quantification has shown for a variety of materials and processing conditions that the microstructural evolution follows a universal pattern of grain subdivision from the macroscale to the nanometer scale. This microstructural evolution has been described empirically and in theoretical models based on general principles for the formation of dislocation structures during plastic deformation by slip. The similarity between the behavior of materials undergoing different deformation patterns forms the basis for future research and development encompassing traditional as well as new materials and processes.

I. INTRODUCTION

IT is a pleasure to be honored with a prize bearing the name of Robert F. Mehl because of his many important contributions to metallurgy and materials science. Especially, I recall his studies of the recrystallization of aluminum The Institute of Metals Lecture, established in 1921, recognizes an outstanding scientific leader who is selected to present a lecture at the TMS Annual Meeting. The Robert Franklin Mehl Award was established in 1972. Niels Hansen is former head of the Materials Research Department at The Risø National Laboratory. He is now with the same Department as Consultant for the Center for Fundamental Research: Metal Structures in Four Dimensions. He received a Masters in chemistry from the Technical University of Denmark, a DEA in metallurgy from the Institute of National Sciences and Technology Nuclear of France, and a Doctor of Technology in materials from the Technical University of Denmark. Dr. Hansen has been recognized for his outstanding research contributions and accomplishments by many major awards, including the following: Member of the Danish Academy of Technical Sciences (1968), Fellow of the Institute of Materials, United Kingdom (1973), Danish Knighthood (1978), Fellow of ASM INTERNATIONAL (1988), Member of Academia Europaea (1993), Foreign Associate, United States National Academy of Engineering (1995), Advisory Professor, Harpin Institute of Technology, China (1995), and the Poul Bergsøe Medal of the Danish Metallurgical Society (2000). METALLURGICAL AND MATERIALS TRANSACTIONS A

in which high-quality and detailed metallographic observations formed the basis for physical modeling of the recrystallization process. This article is indirectly related to the field of recrystallization; it is about microstructures introduced during a deformation process, which are the necessary conditions for the recrystallization process to take place. Deformation microstructures have been investigated since the invention of light microscopy and progress has since been closely related to the development of microscopical techniques, where transmission electron microscopy has been central in the last 50 years. This long history of deformation microst

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