Experimental parameters influencing grain refinement and microstructural evolution during high-pressure torsion
TL;DR: In this paper, a simple model is proposed to explain the development of a homogeneous microstructure in high pressure torsion (HPT) processing of pure nickel samples, showing that the distributions of grain boundary misorientations are similar in the center and at the periphery of the samples.
About: This article is published in Acta Materialia.The article was published on 2003-02-07. It has received 704 citations till now. The article focuses on the topics: Grain boundary & Grain size.
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TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.
3,828 citations
TL;DR: In this article, a 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.
3,669 citations
TL;DR: High pressure torsion (HPT) is a well-known technique for metal forming as discussed by the authors, where samples are subjected to a compressive force and concurrent torsional straining.
2,499 citations
TL;DR: In this article, an overview of recent achievements and new trends in the production of bulk ultrafine-grained (UFG) materials using severe plastic deformation (SPD) is presented.
Abstract: This overview highlights very recent achievements and new trends in one of the most active and developing fields in modern materials science: the production of bulk ultrafine-grained (UFG) materials using severe plastic deformation (SPD). The article also summarizes the chronology of early work in SPD processing and presents clear and definitive descriptions of the terminology currently in use in this research area. Special attention is given to the principles of the various SPD processing techniques as well as the major structural features and unique properties of bulk UFG materials that underlie their prospects for widespread practical utilization.
1,345 citations
TL;DR: A brief overview of the recent progress made in improving mechanical properties of nanocrystalline materials, and in quantitatively and mechanistically understanding the underlying mechanisms is presented in this paper.
994 citations
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TL;DR: In this article, the authors present methods of severe plastic deformation and formation of nanostructures, including Torsion straining under high pressure, ECA pressing, and multiple forging.
5,763 citations
TL;DR: In this paper, a superimposed dislocation network is proposed for the cubic system, which is a natural extension of previous dislocation models and models based on coincidence relationships, and explains many of the observed properties of grain boundaries.
1,665 citations
TL;DR: In this article, experiments were conducted on high purity aluminum to investigate the process of grain refinement during equal-channel angular (ECA) pressing, where samples were subjected to 1 to 4 pressings and then sectioned for microstructural examination in three mutually perpendicular directions.
1,135 citations
TL;DR: In this paper, a combination of high strength and high ductility produced in metals subject to severe plastic deformation (SPD) was shown to enable deformation by newmechanisms.
Abstract: It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.
1,046 citations
31 Aug 1993-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the formation of a special grain boundary phase, i.e., a thin near-boundary layer with high dynamic activity of atoms, has been found, leading to the manifestation of promising new elastic, strength, superplastic, damping and magnetic properties of UFG materials.
Abstract: Strain-heat methods of obtaining ultrafine-grained (UFG) metallic materials with grain sizes as small as 20 nm and peculiarities of their structure are considered. It is shown that intercrystalline boundaries are the main element of the structure of UFG materials and that they are typically in a non-equilibrium state. The formation of a special grain boundary phase, i.e. a thin near-boundary layer with high dynamic activity of atoms, has been found. This unusual structure leads to the manifestation of promising new elastic, strength, superplastic, damping and magnetic properties of UFG materials.
918 citations