This special issue is edited to summarize recent research activity associated with severe plastic deformation (SPD). It is well known that significant refinement of microstructures is achieved in metallic materials using the SPD processes such as Equal-Channel Angular Pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT). High strength is attained without losing much of the ductility for the SPD-processed materials. Superplasticity may also appear because the grain size is reduced to the submicrometer range using the SPD processes. This special issue includes research results on such subjects.
In this special issue, emphasis is placed on the role of lattice defects. It is well established that plastic deformation introduces varieties of lattice defects such as vacancies, dislocations and grain boundaries. Population of these defects increases as the magnitude of the plastic deformation is larger. However, it is not known what happens if an enormous amount of the lattice defects is generated by the SPD processes and why the significant microstructural refinement and associated unusual mechanical properties appear in the SPD-processed materials. There is an ongoing research project in the priority area of a Grant in Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (so-called Monbusho Grant) in Japan. This national project has started in September 2006 under the title of ``Giant Straining Process for Advanced Materials Containing Ultra-High Density Lattice Defects''. The objectives of the project have two folds. The one is to examine mechanisms of microstructural refinement when severe strain is imposed on the samples and the other is to investigate mechanisms for the unusual and unique mechanical properties that the strength and ductility are both improved. We hope that this special issue serves to provide many basic results and related information for the achievement of the objectives. We also hope that superior properties of the SPD processed materials introduced in this special issue can attract many scientists and engineers for further development in the SPD research fields.
We would like to express our great thanks to all authors who contributed to providing very latest information from their research activity. Our thanks are also given to reviewers taking their valuable time to make many useful comments and suggestions.
November 22, 2007
(Received ; Accepted ; Published )
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