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J.W. Christian

Bio: J.W. Christian is an academic researcher from University of Oxford. The author has contributed to research in topics: Crystal & Nucleation. The author has an hindex of 10, co-authored 16 publications receiving 8273 citations.

Papers
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Journal ArticleDOI
01 Jan 1951-Nature
TL;DR: The structure of the brittle intermediate Σ-phase in the system iron-chromium has not yet been determined; but isomorphous phases have been found in the systems iron-vanadium, cobalt and iron-molybdenum as discussed by the authors.
Abstract: THE structure of the brittle intermediate Σ-phase in the system iron–chromium has not yet been determined; but isomorphous phases have been found in the systems iron–vanadium1, cobalt–chromium2 and iron–molybdenum3. All these phases occur at or near to the equiatomic composition, and this has led K. W. Andrews4 to suggest that they are connected with superlattice formation. Recent work in this Laboratory has led to the discovery of four new Σ-phases the compositions of which are of interest. The existence of two of these phases was predicted by Beck and Manly5.

31 citations

Book ChapterDOI
01 Jan 2002
TL;DR: The theory of dislocations was introduced in this article, where the authors show that deformation occurs by the slipping or gliding of closely packed atomic planes over one another, and that the component of the applied shear stress acting across the glide plane and resolved along a closely packed direction of this plane must exceed a certain value.
Abstract: This chapter introduces the theory of dislocations. A dislocation is characterized principally by its Burgers vector, the scalar magnitude that is also called the strength of the dislocation. The Burgers vector is constant along any dislocation line, but this invariant characteristic is not sufficient to specify completely the properties of the discontinuity. The line defect that is called a dislocation contains great importance in the description of almost all solid-state phenomena. For many years the existence of dislocations was inferred rather than observed, and the theory of dislocations was developed during this time into a reasonably well-ordered body of knowledge. More recently, experimental techniques have been devised by means of which individual dislocations may be seen and their properties studied directly, and the most important advances are now being made in this way. Experimental results show that deformation occurs by the slipping or gliding of closely packed atomic planes over one another. Before this gliding can begin, the component of the applied shear stress acting across the glide plane and resolved along a closely packed direction of this plane must exceed a certain value.

30 citations

Book ChapterDOI
01 Jan 2002
TL;DR: The theory of nucleation by random fluctuations in a metastable assembly is due mainly to Volmer and to Becker and Doring as mentioned in this paper, but many other workers have made significant contributions.
Abstract: This chapter introduces the classical theory of nucleation and deals only with transformations that do not involve changes of composition; the complications. The chapter begins with the vapour-liquid transformation where there are no strain energies to be considered. The kinetics of a heterogeneous reaction can be described in terms of the separate nucleation and growth of the transformed regions. The classical theory of nucleation by random fluctuations in a metastable assembly is due mainly to Volmer and to Becker and Doring, but many other workers have made significant contributions. This theory was formulated first for the simplest nucleation process, the condensation of a pure vapour to form a liquid. The essential driving force for a phase transformation is the difierence in the free energies of the initial and final configurations of the assembly, but when small particles of the new phase are formed, the free energy rises at first. Additional factors also have to be considered in transformations in the solid state, where the volume change associated with the transformation, and the possible tendency for the two phases to remain coherent across the interphase boundary, may both produce considerable perturbations of the atomic arrangement.

27 citations

Book
01 Jan 1975

22 citations


Cited by
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Journal ArticleDOI
Akihisa Inoue1
TL;DR: In this article, the authors investigated the stabilization properties of the supercooled liquid for a number of alloys in the Mg-, lanthanide-, Zr-, Ti-, Fe-, Co-, Pd-Cu- and Ni-based systems.

5,173 citations

Journal ArticleDOI
TL;DR: In this article, a selfconsistent and logical account of key issues on Ti-Ni-based alloys from physical metallurgy viewpoint on an up-to-date basis is presented.

3,484 citations

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, a new analysis tool was developed to quantify the experimentally observed changes in morphology of portlandite, allowing the calculation of the relative surface energies of the crystal facets.

2,498 citations

Journal ArticleDOI
TL;DR: In this article, the authors explore a theoretical approach to these fine phase mixtures based on the minimization of free energy and show that the α-phase breaks up into triangular domains called Dauphine twins which become finer and finer in the direction of increasing temperature.
Abstract: Solid-solid phase transformations often lead to certain characteristic microstructural features involving fine mixtures of the phases. In martensitic transformations one such feature is a plane interface which separates one homogeneous phase, austenite, from a very fine mixture of twins of the other phase, martensite. In quartz crystals held in a temperature gradient near the α-β transformation temperature, the α-phase breaks up into triangular domains called Dauphine twins which become finer and finer in the direction of increasing temperature. In this paper we explore a theoretical approach to these fine phase mixtures based on the minimization of free energy.

1,488 citations