Superplasticity

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.

Contenu

1. Historical Introduction.- 1.1 First Observations of Structural Superplasticity.- 1.2 Early Observations of Environmental Superplasticity.- 1.3 The Revival of Interest in Structural Superplasticity.- 2. The Mechanics of Superplastic Deformation and the Assessment of Superplastic Behaviour.- 2.1 The Tensile Test.- 2.2 Constitutive Relations for Superplastic Materials.- 2.3 The Deformation Behaviour of Superplastic Materials.- 2.3.1 The tensile stress-strain curve.- 2.3.2 Tensile stress-strain rate variations.- 2.3.3 Compressive behaviour.- 2.3.4 Torsion testing.- 2.4 The Shape of the Deforming Specimen.- 2.5 Plastic Instability.- 2.5.1 The onset of necking.- 2.5.2 The geometry of neck formation.- 2.6 The Elongations of Rate-Sensitive Materials.- 2.7 The Strain-rate Sensitivity Index, m.- 2.7.1 Determination of m from the $${\sigma _t} - {\dot \varepsilon _t}$$ curve.- 2.7.2 Determination of m using change in strainrate method.- 2.7.3 Determination of m from stress-relaxation tests.- 2.7.4 Comparison of m values determined using different techniques.- 2.7.5 The physical significance of m value measurements.- 2.8 Strain-rate Sensitivity in Environmentally Superplastic Materials.- 2.9 Other Test Procedures for Studying Structural Superplasticity.- 2.9.1 Indentation tests.- 2.9.2 Measurement of internal stresses.- 2.9.3 Measurement of grain boundary shear.- 2.9.4 Damping characteristics.- 2.9.5 Miscellaneous tests.- 3 Structural Superplasticity - Experimental.- 3.1 The Mechanical Properties.- 3.1.1 Characteristics of deformation.- 3.1.2 Necessary conditions.- 3.1.3 Variables of deformation.- (a) Strain-rate.- (b) Strain.- (c) Strain-rate sensitivity index.- (d) Temperature.- 3.1.4 The influence of prior treatments and compositional variations.- 3.1.5 Elongation.- 3.1.6 Macroscopic characteristics: an assessment.- 3.2 Microstructural Studies.- 3.2.1 Qualitative metallography.- (a) Surface studies.- (b) Internal structure.- (c) P.Iarker experiments.- (d) Dynamic experiments.- 3.2.2 Quantitative metallography.- (a) Grain boundary sliding.- (b) Measurements of grain size and shape.- (c) Analysis of texture.- 3.2.3 Assessment of metallographic and topological features.- 3.3 Fracture.- 3.3.1 Macroscopic aspects.- 3.3.2 Microscopic aspects.- 3.3.3 Origin of cavitation.- (a) Phenomenological.- (b) Microstructural.- 4. Structural Superplasticity - Theoretical.- 4.1 Early Theories.- 4.2 Modern Theories.- 4.2.1 Rheological theories.- 4.2.2 Activation energy for superplastic flow.- 4.2.3 Atomistic theories.- (a) Diffusional flow mechanisms.- (b) Dislocation creep theories.- (c) Grain boundary deformation models.- (d) Multi-mechanisms.- 5. Environmental Superplasticity.- 5.1 Experimental Results.- 5.1.1 Macroscopic characteristics.- (a) Transformational plasticity.- (b) Temperature cycling.- (c) Neutron irradiation.- 5.1.2 Metallographic features.- 5.2 Theoretical Studies.- 5.2.1 Phenomenological approaches.- 5.2.2 Mechanistic models.- 5.2.3 Cavitation.- 6. Applications of Superplasticity.- 6.1 Forming Operations.- 6.1.1 Hydraulic bulging.- 6.1.2 Sheet thermoforming.- 6.1.3 Blow moulding.- 6.1.4 Deep drawing.- 6.1.5 Punch stretching.- 6.1.6. Forging and stamping.- 6.1.7 Extrusion.- 6.1.8 Dieless drawing.- 6.1.9 Powder metallurgy processes.- 6.2 Theoretical Analyses of Superplastic Forming Processes.- 6.2.1 Analysis of hydraulic bulging.- 6.2.2 Analysis of bulging into a 90° V-groove.- 6.2.3 Analysis of extrusion.- 6.2.4 Regression analyses.- 6.3. Practical Developments.- 6.3.1 Alloys.- 6.3.2 Design considerations.- 6.3.3 Tooling.- References.- Author Index.