Superplasticity and Grain Boundaries in Ultrafine-Grained Materials

Contents:

Introduction • Structural Superplasticity of Polycrystalline Materials • Structural levels, spatial scales and description levels • Structural superplasticity: from the combination of mechanisms to cooperative grain boundaries sliding • Structural superplasticity: from meso-description to macrocharacteristics • References

Characteristics of Grain Boundary Enesembles • Crystal geometry and structure of intercrystalline boundaries • Methods for describing the structure of the grain boundaries • Analytical representation of the basis of the coincident-site lattice for cubic lattices • Special grain boundaries in the monoclinic lattice • Description of the grain boundary misorientation distribution (GBMD) • Computer model of a polycrystal. A calculation algorithm • References

Orientation-Distributed Parameters of the Polycrystalline Structure ? The distribution function of the grains with respect to crystallographic orientations. Calculation methods • Relationship between the grain boundary misorientation distribution and the ODF • Correlation orientation of adjacent grains. The concept of the basis spectra of misorientation of the grain boundaries • Modelling the misorientation spectra of the grain boundaries in the FCC crystals with modelling ODF • References

Experimental Investigations of Grain Boundary Ensembles in Polycrystals • Diffraction methods of measuring misorientation • Methods of measuring the misorientation of two adjacent grains • The experimental measurement error • Experimental spectra of the grain boundaries in FCC polycrystals • Orientation distribution function in nichrome. Experimental and modelling GBMDs • Orientation distribution function in nichrome and stainless steels • Modelling spectra of the misorientation of the grain boundaries in nichrome and AISI stainless steels Comparison with the experimental results • Special features of the grain boundaries in the FCC materials with a high stacking fault energy • Rolling and annealing texture of aluminium • Grain boundary and samples in aluminium: experiments and modelling • References

Grain Boundary Sliding in Metallic BI- and Tricrystals • Dislocation nature of grain boundary sliding (GBS) • Formulation of the model of stimulated grain boundary sliding • Formal solution and its analysis • Special features of pure grain boundary sliding • Local migration of the grain boundary as the mechanism of reorganisation of the triple junction. Weak migration approximation • Variance formulation of the system of equations for the shape of the boundary and pile-up density • The power of pile-ups of grain boundary dislocations • References

Percolation Mechanism of Deformation Processes in Ultrafine-Grained Polycrystals • Percolation mechanism of the formation of a band of cooperative grain boundary sliding • Conditions of formation of CGBS bands as the condition of realisation of the superplastic deformation regime • Shear rate along the CGBS band • Kinetics of deformation in CGBS bands • Comparison of the calculated values with the experimental results • References

Percolation Processes in a Network of Grain Boundaries Ultrafine-Grained Materials • Effect of grain boundaries on oxidation and diffusion processes in polycrystalline oxide films • High-resolution electron microscopy of zirconium oxide: grain clusters, surrounded only by special boundaries • Effect of the statistics of the grain boundaries on diffusion in zirconium oxide • Special features of oxidation kinetics under the effect of stresses at the metal/oxide boundary • Texture and spectrum of misorientation of the grain boundaries in a NiO film on (100) and (111) substrates:?modelling and experiments • References

Microstructure and Grain Boundary Ensembles in Ultrafine-Grained Materials • Methods of producing ultrafine-grained and nanostructured materials by severe plastic deformation • Effect of the parameters of quasi-hydrostatic pressure on the microstructure and grain boundary ensembles in nickel • Spectrum of misorientation of grain boundaries in ultrafine-grained nickel • Advanced methods of automatic measurement of the grain boundary parameters • The misorientation distribution of the grain boundaries in ultrafine-grained nickel. Experiments and modelling • References

Grain Boundary Processes in Ultrafine-Grained Nickel and Nanonickel • Grain growth kinetics in ECAP specimens • Activation energy and stored enthalpy in ultrafine-grained nickel • Evolution of the microstructure and texture in HPT nickel in annealing • Superplasticity of nanocrystalline nickel • References

Duration of the Stable Flow Stage in Superplastic Deformation • Superplastic capacity and the rate sensitivity parameter • Description of thickness differences of a flat specimen in tensile deformation • Formation of thickness difference as a random process • Absorption condition and the equation for limiting strain • Some properties of limiting strain ?References

Derivation of Constitutive Equations In Multicomponent Loading Conditions • From the deformation mechanism to constitutive equations • Kinematics of polycrystalline continuum • Strain rate tensor determined by shear along the CGBS bands • Degenerate cases and variants of coaxiality of the tensors • References

Conclusion • Index

About the Authors: 

Alexander Zhilyaev (PhD., Dr.Sci.) is a Principal Research Scientist of the Institute for Metals Superplasticity of Russian Academy of Science (Ufa, Russia) and currently Ram??n y Cajal Fellow with the Centro Nacional de Investigaciones Metal??rgicas (CENIM, CSIC, Madrid, Spain) graduated from Bashkir State University (Ufa, Russia) in 1981. Current research interests are microstructure and properties of ultrafine-grained and nanostructured pure metals, alloys and ceramics processed by means of severe plastic deformation. He is author and co-author of three books and more than 100 publications.

Anatoly Pshenichnyuk (PhD., Dr.Sci.) is a Head of the laboratory for Mechanics of Plastic and Superplastic Flow of Alloys of the Institute for Metals Superplasticity of Russian Academy of Science (Ufa, Russia) graduated from Bashkir State University (Ufa, Russia) in 1971. Current research interests are macroscale cooperative phenomena and properties of ultrafine-grained and nanostructured materials and non-linear physics. He is author and co-author of one book and about 100 publications.