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Über dieses Buch

This is the second book in a new series - "Materials Research and Engineering" - devoted to the science and technology of materials. "Materials Research and Engineering" evolves from a previous series on "Reine und Allgemeine Metallkunde", which was edited by Werner KBster until his eightieth birthday in 1976. Although the present series is an outgrowth of the earlier one, it should not and cannot be regarded as a continuation. There had to be a shift of scope - and a change in presenta­ tion as well. Metallurgy is no longer an isolated art and science. Rather, it is linked by its scientific basis and technological implications to non-metallic and composite materials, as well as to processes for production, refining, shaping, surface treatment, and application. Thus, the new series, "Materials Research and Engineering", will present up-to-date information on scientific and technological pro­ gress, as well as on issues of general relevance within the engineering field and industrial society. Following the general position analysis of materials in the present world as given in volume 1, now volume 2 focuses on a special topic: It provides a thorough treatment of theoretical, experimental, and applied aspects of superplasticity.

Inhaltsverzeichnis

Frontmatter

1. Historical Introduction

Abstract
Superplasticity is the deformation process that produces essentially neck-free elongations of many hundreds of percent in metallic materials deformed in tension. High ductilities are also encountered in ‘superplastic’ alloys during torsion, compression and indentation hardness testing. Further, these materials are characterised by very low strengths.
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

2. The Mechanics of Superplastic Deformation and the Assessment of Superplastic Behaviour

Abstract
The significant suggestion of Backofen, Turner and Avery(42) that the basis of superplastic flow is to be found in the strain-rate sensitivity of flow stress is now known to apply equally to structurally as well as environmentally superplastic materials. In this Chapter the nature of the tensile test is first examined briefly. This is followed by a discussion of plastic stability and the rationalization of the phenomenology of superplastic flow in terms of a number of empirical and semi-empirical equations that have been proposed to analyse this mode of deformation. Subsequently the various methods of evaluating strain-rate sensitivity (SRS) in materials being deformed in tension will be described and also compared with other available procedures of determining this flow characteristic. The chapter will conclude with an account of some other specialised techniques, e.g. the examination of grain boundary sliding, of importance in assessing the extent of development of superplastic behaviour.
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

3. Structural Superplasticity — Experimental

Abstract
In Chapter 1 the historical aspects of studies in superplasticity were discussed and the Chapter concluded with a description of the revival of interest in structural superplasticity following developments in 1962 and 1964. In this chapter the contemporary experimental evidence for the many characteristics of structural superplasticity will be examined. Attention will be concentrated on work carried out subsequent to the dates given above. In some special cases it may be necessary to make reference to early work but this should only be so when unique alloys have been used or when observations have been made which have not been since repeated. In addition, it was not considered appropriate to include in this chapter much of the Russian work not available in translation. The theoretical explanations which have been put forward to account for structural superplasticity will be considered in Chapter 4.
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

4. Structural Superplasticity — Theoretical

Abstract
It was mentioned in Chapter 1 that early Russian workers attempted to explain the occurrence of structural superplasticity in terms of solution-precipitation reaction or the development of metastability. Underwood (4) has discussed these early theories in detail. In view of their historical importance these theories are briefly reviewed in Section 4.1.
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

5. Environmental Superplasticity

Abstract
In Section 1.2 the discovery of transformational plasticity and the early work in this area up to late 1950’s was described. As briefly noted in that section environmental superplasticity is caused by any one of the three methods:
(i)
thermal cycling of a material through a phase change with concurrent application of a small external stress,
 
(ii)
thermally cycling a material with anisotropic coefficients of thermal expansion while simultaneously applying a load, and
 
(iii)
subjecting a material under a small stress to neutron irradiation.
 
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

6. Applications of Superplasticity

Abstract
As described in the previous Chapters the characteristic features of the deformation of alloys which exhibit structural superplasticity is that extremely high strains can be achieved with low applied stresses with a high strain-rate sensitivity during deformation. The high strain-rate sensitivity makes these alloys resistant to localised deformation (necking or thinning). Thus it is not surprising that at an early stage it was concluded that these features could be taken advantage of in forming operations of various types. The resemblance between the behaviour of superplastic materials and thermoplastics above their glass transition temperature is clear both in their stress-strain and stress-strain rate dependence, and this suggested that forming techniques for the latter could readily be adopted for the former. Thus it was envisaged that processes such as vacuum thermoforming, drape forming, bottle-blowing etc., could be utilised for forming superplastics.
Kuppuswamy Anantha Padmanabhan, Graeme John Davies

Backmatter

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