Ti-Nb-Ta-Zr Alloy Rolling Deformation Texture

TiNbTaZr alloy is potential medical biomaterials, due to its high strength, low elastic modulus, superelasticity, superplasticity, and many other excellent performances. TiNbTaZr rolling samples under solid solution state and deformation state were characterized by TEM and XRD technologies. The results show that the alloy has the grain size of 42mm, straight of grain boundaries, intragranular no significant defects after solution heat treatment at 1063K. When the deformation reaches 40% in the rolling process, the local zones in intragranular appears high density of dislocations and a small amount of twinning. When the rolling is to 92%, the high density of dislocation cells forms nano subgrain block in sample with {100} plate texture and the texture axis of {100} plate under density of 2.29.

Electron Diffraction Investigation of Crystallographic Texture of Thin Films

ABSTRACTA method of investigating thin film crystallographic texture by electron diffraction is reviewed. The reciprocal lattices of fibrous and lamellar textured thin films are spherical belts around the texture axis. Equations describing the projection of the spherical belts onto the Ewald sphere along the texture axis direction are presented. Based on these equations the geometric and intensity evolution of the electron diffraction patterns with the tilt angle about an arbitrary axis in the film plane can be analyzed in a systematic way. The geometric characteristics of the electron diffraction patterns are then used to derive the texture axis directional index and its angular distribution. The way to determine the equal-intensity circular arcs on the diffraction pattern is also discussed. This method can be applied to both single layered and multilayered thin films of various applications.

Texture and Thermal Expansion Anomalies of B19'-Martensite in Tensile Deformed TiNi Shape Memory Alloy

The dilatometric studies of Ti-50.5 at.% Ni alloy have shown that the thermal expansion coefficient (TEC) of B19'-martensite varies considerably for the solution-treated and tensile-strained samples. In the undeformed state the TEC has the positive value α=9.7.10-6 K-1. After tensile straining the TEC decreases sharply and takes on a negative value (down to – 10.8.10-6 K-1). The reasons for the variation of the TEC of the B19'-phase of the solution-treated and deformed samples are discussed. The tensile straining was found to create in the samples an extremely sharp texture of the phase transformation, with the texture axis parallel to the strain direction. The TEC of monoclinic B1939;-lattice is different in various crystallographic directions and assumes a negative value in the [0 01]B19' direction.

Defect Structure and Crystallographic Texture of Polycrystalline Electrodeposits

ABSTRACTThe polycrystalline electrodeposits of metals and alloys are characterized by exceptionally fine, equiaxed grain structure; the grain sizes two to four orders of magnitude smaller than those encountered in the bulk metals are generally obtained. Under the conditions of high cation discharge rate, twins accommodate interface growth; elongated grains and columnar morphology then become the common features. The dislocation density can be very high; the dislocations reside primarily as complex substructural configurations which are inherently unstable to thermal or mechanical stimuli. Vacancies, microvoids and vacancy/impurity complexes are endemic to deposits. The defect structure infrastructure (dislocation density and configuration, twinning frequency and hydrogen bubbles) is controlled by the deposition overpotential which also determines the preferred crystallographic texture. When the texture axis is parallel to the twin plane, anisotropie grain structure and columnar morphology are promoted; when the texture axis is perpendicular to the twin plane, a layered structure forms. The textured electrodeposit generates a duplex grain and subgrain structure. The random grains are small and defect saturated; the oriented grains are much larger and relatively free from crystal defects. The incidence of random grains, their size and defect concentration also depend upon the melting temperature of the metal.

A New Approach to Describing Three-Dimensional Orientation Distribution Functions in Textured Materials—Part II: Model ODF for Rolling Textures

Sections of a three-dimensional Orientation Distribution Function (ODF) for the α-Fe rolling texture typical for most b.c.c. metals have been constructed on the basis of the proposed new method for ODF simulation through the representation of a crystallite orientation by nine rotations, only three of which are varied for a given component. The description of texture by superposition of partial fibre components in used. A comparison of such a model ODF with an ODF reconstructed from experimental pole figures by series expansion is presented. As a result all really encountered textures can be simulated by variation of the crystallite spread parameters, texture axis positions, and predominant preferred orientations in terms of a common approach.

A New Approach to Describing Three-Dimensional Orientation Distribution Functions in Textured Materials–Part I: Formation of Pole Density Distribution on Model Pole Figures

New method for simulation of orientation distribution functions of textured materials has been proposed. The approach is based on the concept to describe any texture class by a superposition of anisotropic partial fibre components. The texture maximum spread is described in a “local” coordinate system connected with the texture component axis. A set of Eulerian angles γ1,γ2,γ3 are introduced with this aim. To specify crystallite orientations with respect to the sample coordinate system two additional sets of Eulerian angles are introduced besides γ1,γ2,γ3. One of them, (Ψ0,θ0,ϕ0), defines the direction of the texture axis of a component with respect to the directions of the cub. The other set, (Ψ1,θ1,ϕ1), is determined by the orientation of the texture component and its texture axis in the sample coordinate system. Analytical expressions approximating real spreads of crystallites in three-dimensional orientation space have been found and their corresponding model pole figures have been derived. The proposed approach to the texture spread description permits to simulate a broad spectrum of real textures from single crystals to isotropic polycrystals with a high enough degree of correspondence.

X-Ray Diffraction of Some Biphenylcyclohexanes (BCH's)

X-ray diffraction measurements have been made on BCH5Cl, BCH5Br, BCH5CN, BCH52 and binary mixture of BCH5CN and BCH52, in the nematic phase. BCH5C1 and BCH5Br are thought to have a weak molecular correlation along the texture axis with repeat unit along that axis of ~ 1.1 molecular lengths. Whereas for BCH5CN the repeat unit along the texture axis is about 1.4 molecular lengths implying a strong molecular association.The d-spacings of the binary mixtures of the strongly polar BCH5CN and the nonpolar BCH52, in the nematic phase, vary roughly linearly between the d-spacing of BCH5CN and that of BCH52.