1,721,055 research outputs found
Processing by severe plastic deformation: an ancient skill adapted for the modern world.
No full textThe processing of bulk solids through the application of severe plastic deformation has now become a well-established procedure for achieving grain refinement to the submicrometer or even the nanometer level. Several basic techniques are currently in place but most attention has been devoted to the procedures of equal-channel angular pressing, high-pressure torsion and accumulative roll-bonding. This paper presents an introductory overview of processing by severe plastic deformation including historical developments and recent new advances in the processing technology. Special emphasis is placed on the move towards the commercialization of the severe plastic deformation approac
Using severe plastic deformation to produce nanostructured materials with superior properties
No full textThe recent decade was marked by significant advances in the development of severe plastic deformation (SPD) techniques to achieve new and superior properties in various materials. This review examines the achievements in these areas of study and explores promising trends in further research and development. SPD processing provides strong grain refinement at the nanoscale, produces high dislocation and point defect densities as well as unusual phase transformations associated with particle dissolution, precipitation or amorphization. Such SPD-induced nanostructural features strongly influence the deformation and transport mechanisms and can produce a substantial enhancement in the performance of advanced materials. Exploiting this knowledge, we discuss the concept of nanostructural design of metals and alloys for multifunctional properties such as high strength and conductivity, superplasticity, increased radiation and corrosion tolerance and others. Special emphasis is placed on advanced metallic biomaterials that promote innovative applications in medicine.Keywords: bulk nanostructured materials, severe plastic deformation, ultrafine-grained biomaterials, functional properties, mechanical properties, nanostructural design<br/
The art and science of tailoring materials by nanostructuring for advanced properties using SPD techniques
No full textIn recent years a breakthrough has developed in the studies of nanostructured metals and alloys as advanced structural and functional materials associated both with the development of new routes for the fabrication of bulk nanostructured materials using severe plastic deformation (SPD) and with investigations of the fundamental mechanisms that lead to the new properties of these materials. This review paper discusses new concepts and principles in using SPD processing to fabricate bulk nanostructured metals with advanced properties. Special emphasis is placed on the relationship between microstructural features and properties, as well as the innovation potential of SPD-produced nanomaterials.<br/
Principles of equal-channel angular pressing as a processing tool for grain refinement
No full textDuring the last decade, equal-channel angular pressing (ECAP) has emerged as a widely-known procedure for the fabrication of ultrafine-grained metals and alloys. This review examines recent developments related to the use of ECAP for grain refinement including modifying conventional ECAP to increase the process efficiency and techniques for up-scaling the procedure and for the processing of hard-to-deform materials. Special attention is given to the basic principles of ECAP processing including the strain imposed in ECAP, the slip systems and shearing patterns associated with ECAP and the major experimental factors that influence ECAP including the die geometry and pressing regimes. It is demonstrated that all of these fundamental and experimental parameters play an essential role in microstructural refinement during the pressing operation. Attention is directed to the significant features of the microstructures produced by ECAP in single crystals, polycrystalline materials with both a single phase and multi-phases, and metal–matrix composites. It is shown that the formation of ultrafine grains in metals and alloys underlies a very significant enhancement in their mechanical and functional properties. Nevertheless, it is demonstrated also that, in order to achieve advanced properties after processing by ECAP, it is necessary to control a wide range of microstructural parameters including the grain boundary misorientations, the crystallographic texture and the distributions of any second phases. Significant progress has been made in the development of ECAP in recent years, thereby suggesting there are excellent prospects for the future successful incorporation of the ECAP process into commercial manufacturing operations
Achieving exceptional grain refinement through severe plastic deformation: new approaches for improving the processing technology
No full textThe processes of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) are now established for the fabrication of ultrafine-grained metals having superior properties by comparison with their coarse-grained counterparts. This article examines the recent developments designed to improve the processing technology of ECAP and HPT and to establish these techniques as viable procedures for use in industrial applications. Based on these developments, it is reasonable to anticipate these processing procedures will experience increasing use in the fabrication of commercial product
The 7th International Conference on Nanomaterials by Severe Plastic Deformation: a report of the International NanoSPD Steering Committee
No full textThe 7th International Conference on Nanomaterials by Severe Plastic Deformation (NanoSPD7) is hosted by the University of Sydney (Australia) following a series of earlier conferences: in Moscow (1999), Vienna (2002), Fukuoka (2005), Goslar (2008), Nanjing (2011) and Metz (2014). This introductory paper reports on several major developments in NanoSPD activities as well as on recent NanoSPD citation data which illustrate the growth and expansion of this important research area for the time period following the conference in Metz. Close attention is given to topics of nanostructuring of metals by SPD processing for advanced properties and on new trends in developing SPD techniques for practical applications. A special concern of the committee is the appropriate terminology that is used in this new field of science and engineering as well as the innovation potential of recent applied studies and developments
Chapter 1 - High-pressure torsion and equal-channel angular pressing
No full textIn this chapter, the main peculiarities of ultrafine-grained (UFG) structure formation in commercially pure Ti is examined when processing by high-pressure torsion (HPT) or equal-channel angular pressing (ECAP). High-pressure torsion is used to produce Ti with extremely small grain sizes (generally < 100 nm). The ECAP technique was developed in the 1990s by R.Z. Valiev and coauthors and successfully used to produce UFG structures in bulk billets of pure Ti. Recently, this technique was further developed and a number of modifications of the technique have been proposed, including continuous ECAP or ECAP-Conform which enables the production of long-length rods (up to 1 m)
A possible stabilizing effect of work hardening on the tensile performance of superplastic materials
No full textIn general, the process of superplastic deformation is regarded as steady-state so that the flow stress is given as a function of the strain rate only, thereby emphasizing the significance of the strain rate sensitivity and its determining methods. In this work, in addition to the important role of the strain rate sensitivity, it is shown that it is necessary also to consider the stability criteria for real, stable superplastic deformation through other factors such as work hardening. A possible scenario is proposed to describe the process whereby the work hardening rate may stabilize the deformation process when a perturbation occurs in the cross-section of the sample. The assumption of a work hardening effect is confirmed by its application for interpretation of the systematic deviations observed between the strain rate sensitivities determined experimentally using different experimental methods.</p
Influence of Zn content on the microstructure and mechanical performance of ultrafine-grained Al-Zn alloys processed by high-pressure torsion
Get PDFAl-Zn alloys were processed by high-pressure torsion (HPT) to produce ultrafine-grained (UFG) materials. For low Zn contents, HPT gave strengthening due to grain refinement while for the highest Zn concentration the decomposition of the microstructure yielded an abnormal softening at room temperature. The microstructure decomposition led also to the formation of a Zn-rich phase which wet the Al/Al grain boundaries and enhanced the role of grain boundary sliding with unusually high strain rate sensitivity. The occurrence of intensive sliding in these UFG alloys is demonstrated by deforming micro-pillars
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