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Journal ArticleDOI

Microstructural aspects of superplasticity

01 Aug 1985-Journal of Materials Science (Kluwer Academic Publishers)-Vol. 20, Iss: 8, pp 2661-2686
TL;DR: The microstructural aspects of the superplastic phenomenon are reviewed in this article, where experimental results of a very large number of investigations are critically analysed in the context of: grain shape and size; grain growth; grain boundary sliding and migration, grain rotation and rearrangement; diffusion and dislocation activity.
Abstract: The microstructural aspects of the superplastic phenomenon are reviewed. The experimental results of a very large number of investigations are critically analysed in the context of: grain shape and size; grain growth; grain boundary sliding and migration, grain rotation and rearrangement; diffusion and dislocation activity. It is shown, that in spite of often conflicting evidence in the literature, a common pattern of microstructural behaviour emerges for all the materials and conditions investigated to date.
Citations
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MonographDOI
06 Nov 2008
TL;DR: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials as discussed by the authors.
Abstract: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials To ensure that the student gains a thorough understanding the authors present the fundamental mechanisms that operate at micro- and nano-meter level across a wide-range of materials, in a way that is mathematically simple and requires no extensive knowledge of materials This integrated approach provides a conceptual presentation that shows how the microstructure of a material controls its mechanical behavior, and this is reinforced through extensive use of micrographs and illustrations New worked examples and exercises help the student test their understanding Further resources for this title, including lecture slides of select illustrations and solutions for exercises, are available online at wwwcambridgeorg/97800521866758

2,905 citations

Journal ArticleDOI
TL;DR: In this article, it is suggested that the absorption of dislocations into grain boundaries (GBs) is due to the migration and sliding of some highly non-equilibrium GBs during the deformation process and is influenced by high level internal stresses.
Abstract: Mechanical behaviour and structural changes, such as the evolution of grain and dislocation structures and the formation of slip lines and grain-boundary-sliding traces, of a submicron-grained (SMG) copper during room-temperature compression have been studied. It is suggested that the absorption of dislocations into grain boundaries (GBs) is due to the migration and sliding of some highly non-equilibrium GBs during the deformation process and is influenced by high level internal stresses. From this point of view, the unusual behaviour of SMG copper, in particular, the high yielding and flow stresses, the absence of strain hardening, high plasticity and low strain rate sensitivity, are explained. Analogies of the mechanical behaviour of SMG copper with mechanical properties of metallic materials at large plastic strains in stage IV are discussed.

476 citations

Journal ArticleDOI
TL;DR: A review of superplasticity in polycrystalline materials can be found in this article, where the authors present an overview of these new developments using the established behavior of conventional metallic alloys as a standard for comparison with the mechanical properties of new materials.
Abstract: The ability to achieve a high tensile ductility in a polycrystalline material is of interest both from a scientific point of view and also because of potential applications in the materials forming industry. The superplasticity of conventional metallic alloys is now well-documented and understood reasonably well. However, the field of superplasticity has expanded recently beyond the traditional metallic alloys to include evidence of superplastic-like behavior in a very wide range of new and advanced materials. To date, superplasticity has been reported in mechanically alloyed metals, metal matrix composites, ceramics, ceramic matrix composites and intermetallic compounds. This review presents an overview of these new developments using the established behavior of conventional metallic alloys as a standard for comparison with the mechanical properties of these new materials. As well be demonstrated, the new materials often exhibit significant differences in their flow characteristics in comparison with the traditional superplastic metallic alloys. The successful utilization of superplastic materials in forming applications requires an understanding of the failure processes occurring in the materials in terms of both the localization of external flow and the accumulation of internal damage through the nucleation and growth of cavities. These problems are also addressed in this review.

427 citations

Journal ArticleDOI
TL;DR: In this article, the superplastic behavior of the composite Y-TZP/Al{sub 2}O{sub 3} (20 wt%) in uniaxial tension has been evaluated.
Abstract: The superplastic behavior of the composite Y-TZP/Al{sub 2}O{sub 3} (20 wt%) in uniaxial tension has been evaluated. Large elongation (>200%) indicated superplasticity. The stress exponent and activation energy of thee composite were found to be the same order with those of Y-TZP. The flow behavior of the composite containing Al{sub 2}O{sub 3} grains could be described by a rheological model as a non-Newtonian flow modified by the second-phase grains. The cavitation damage and the creep crack growth could be reduced by keeping the strain rate low enough that a specimen elongated 100% at elevated temperature maintained a strength of 1,800 MPa at room temperature.

165 citations

Journal ArticleDOI
TL;DR: A review of the major characteristics of superplasticity in ceramics can be found in this paper, where it is shown that there are both similarities to and differences from metals.
Abstract: It is now recognized that superplasticity is a potential deformation process in ceramics. This review summarizes the major characteristics of superplasticity and examines the reports of both transformation and structural superplasticity in ceramic and other non-metallic materials. It is shown that there are both similarities to and differences from metals. Similarities include the variation of strain rate with stress and grain size, but an important difference is the necessity to consider the role of intergranular glassy phases in ceramics. Superplasticity is also important in intermetallic compounds, and in geological materials where there is evidence for superplastic deformation both in laboratory experiments and in natural deformation.

128 citations

References
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Book
01 Jan 1972
TL;DR: Physical Metallurgy Principles as mentioned in this paper is intended for use in an introductory course in physical metallurgy and is designed for all engineering students at the junior or senior level and is largely theoretical, but covers all aspects of physical metelurgy and behavior of metals and alloys.
Abstract: Physical Metallurgy Principles is intended for use in an introductory course in physical metallurgy and is designed for all engineering students at the junior or senior level. The approach is largely theoretical, but covers all aspects of physical metallurgy and behavior of metals and alloys. The treatment used in this textbook is in harmony with a more fundamental approach to engineering education.

2,265 citations

Book
01 Jan 1975

1,385 citations

Journal ArticleDOI
TL;DR: In this article, a new mechanism for superplastic deformation is described and modelled, which differs fundamentally from Nabarro-Herring and Coble creep in a topological sense: grains switch their neighbors and do not elongate significantly.

1,307 citations

Journal ArticleDOI
01 Apr 1971
TL;DR: In this paper, the problem of sliding at a nonplanar grain boundary is considered in detail, and the results give solutions to the following problems: 1) How much sliding occurs in a polycrystal when neither diffusive flow nor dislocation motion is possible? 2) What is the sliding rate at a wavy or stepped grain boundary when diffusional flow of matter occurs? 3) How is the rate of diffusional creep in polycrystals in which grain boundaries slide? 4) how is this creep rate affected by grain shape, and grain boundary migration? 5)
Abstract: The problem of sliding at a nonplanar grain boundary is considered in detail. The stress field, and sliding displacement and velocity can be calculated at a boundary with a shape which is periodic in the sliding direction (a wavy or stepped grain boundary): a) when deformation within the crystals which meet at the boundary is purely elastic, b) when diffusional flow of matter from point to point on the boundary is permitted. The results give solutions to the following problems. 1) How much sliding occurs in a polycrystal when neither diffusive flow nor dislocation motion is possible? 2) What is the sliding rate at a wavy or stepped grain boundary when diffusional flow of matter occurs? 3) What is the rate of diffusional creep in a polycrystal in which grain boundaries slide? 4) How is this creep rate affected by grain shape, and grain boundary migration? 5) How does an array of discrete particles influence the sliding rate at a grain boundary and the diffusional creep rate of a polycrystal? The results are compared with published solutions to some of these problems.

1,101 citations

Journal ArticleDOI
M.F. Ashby1
TL;DR: The behavior of atoms in a grain or phase boundary when the boundary slides (when the crystals which meet at the boundary suffer a relative shear displacement parallel to the boundary plane) and during diffusional creep is described in this article.

364 citations