Deformation Mechanisms of Alpha-Uranium Single Crystals

Lloyd, L.T.; Chiswik, H.H.

doi:10.1007/bf03379029

Cited by 9 publications

(13 citation statements)

References 4 publications

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“…A clear example is given by orthorhombic uranium, for which some interesting data are available. The experimental • literature reports five twinning modes, two of which are conjugate (see Cahn, 1953;Lloyd & Chiswik, 1955;Daniel, Lesage & Lacombe, 1971;Crocker, 1965). These modes are now well accepted in the literature (see Klassen-Nekliudova, 1964, p. 168;Barrett & Massalski, 1966, p. 415;Kelly & Groves, 1970, p. 303).…”

Section: Uraniummentioning

confidence: 94%

The Cauchy–Born Hypothesis, Nonlinear Elasticity and Mechanical Twinning in Crystals

Zanzotto¹

1996

Acta Cryst Sect A

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The bridge between the molecular descriptions of crystalline configurations and the continuum theories of crystal mechanics such as linear and nonlinear elasticity is given by a natural hypothesis that goes back to Cauchy and Born, referred to as the 'Born rule'. This paper reports on an extensive investigation on the validity of the Born rule and the possibility of applying nonlinear elasticity to describe the behavior of crystalline solids. This is done by studying the phenomenon of mechanical twinning and its implications for the invariance group of the energy density of the crystal. The analysis leads to the conclusion that, in the 'generic' case, the Born rule does not hold and that nonlinear elasticity theory cannot provide an adequate model for crystal mechanics because an unphysical energy invariance is derived. However, the Born rule works and elasticity theory can be used for crystals whose twinning shears satisfy certain quite restrictive 'nongeneric' conditions. Relevant experimental data confirm these theoretical negative conclusions. It is remarkable that two very important classes of 'nongeneric' materials to which an elastic model safely applies do emerge experimentally: shape-memory alloys and materials whose crystalline structure is given by a simple Bravais lattice.

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Section: Uraniummentioning

confidence: 94%

The Cauchy–Born Hypothesis, Nonlinear Elasticity and Mechanical Twinning in Crystals

Zanzotto¹

1996

Acta Cryst Sect A

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“…[34] The (172) twins, however, have only been observed as deforThe intergranular lattice strains ( a , b , c ) are also shown during unloading in Figure 10 (open symbols). They do not mation twins in pure uranium (by two different investigators [34,41] ) and are not theoretically predicted to occur during remain constant as the applied stress is removed, as would transformation. [42] The lenticular form of these twins, combined with their association only with deformation, indicates that they are nucleated during deformation.…”

Section: B Transmission Electron Microscopymentioning

confidence: 95%

Uniaxial tensile deformation of uranium 6 wt pct niobium: A neutron diffraction study of deformation twinning

Brown

Bourke

Stout

et al. 2001

Metall Mater Trans A

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The deformation of polycrystalline uranium 6 wt pct niobium (U6Nb) was studied in situ during uniaxial tensile loading by time-of-flight neutron diffraction. Diffraction patterns were recorded at incremental stresses to a maximum of 450 MPa (ϳ4 pct macroscopic strain). Consistent with reorientation of the martensite variants by twinning, significant changes in the diffraction peak intensities, which were proportional to the plastic contribution of the macroscopic strain, were observed. Both the lattice parameters (a, b, c, and ␥) and interplanar spacings (d hkl ) were determined as a function of applied stress. Phenomenologically, the highly anisotropic stress response of the lattice parameters as well as the individual lattice spacings can be related to deformation twinning. Preliminary transmission electron microscopy (TEM) studies identified the (130) and (172) as active deformation twinning systems of U6Nb in tension.

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“…(22) They were grown by the grain coarsening technique described by Fisher. (23) Each crystal was isolated from other grains and prepared for compression in a specific crystallographic direction by normal X-ray Laue backreflection and uranium metallographic techniques.…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…There was strong evidence for the grouping of (lOO) poles of recrystallized grains near the {llO} poles of the original crystal orientation and the {llO} poles of its [130] twin orientations. Three of these groups are obvious in Figure 10; they are: orientations number (l3, 16,21,30,35,38,43,45,46); (26,27,28,37) and (22,23,25,32,47). The first two groups lie near the (llO) pole of the original crystal orientation, since the (llO) pole is identical to the (llO) pole.…”

Section: A Orientation Relationshipsmentioning

confidence: 99%

“…Figure 22a represents the orientation relationship for eight grains found upon annealing a crystal deformed by tension in a <231> direction. From considerations of the operative deformation mechcinisms at room temperature, (22) this crystal was probably not deformed by twinning, but it should have deformed by kinking; this is the type of deformation the authors have reported. The orientation relationship found by Calais et al, agrees well with the one observed in the present work.…”

mentioning

confidence: 92%

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RECRYSTALLIZATION OF DEFORMED ALPHA-URANIUM SINGLE CRYSTALS. Final Report- -Metallurgy Division Program 4.1.19. Work Completed-January 1, 1956

Lloyd¹

1959

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Deformation Mechanisms of Alpha-Uranium Single Crystals

Cited by 9 publications

References 4 publications

The Cauchy–Born Hypothesis, Nonlinear Elasticity and Mechanical Twinning in Crystals

The Cauchy–Born Hypothesis, Nonlinear Elasticity and Mechanical Twinning in Crystals

Uniaxial tensile deformation of uranium 6 wt pct niobium: A neutron diffraction study of deformation twinning

RECRYSTALLIZATION OF DEFORMED ALPHA-URANIUM SINGLE CRYSTALS. Final Report- -Metallurgy Division Program 4.1.19. Work Completed-January 1, 1956

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