Texture Volume Fractions Research Articles

Comparison of the texture evolution in cold rolled DC and SC AA 5182 aluminum alloys

The hot bands of direct chill cast (DC) and strip cast (SC) AA 5182 aluminum alloys were annealed at 454 °C for 3 h, and then cold rolled to different reductions. The ODFs of the cold rolled samples were determined by X-ray diffraction in order to compare the texture evolution of DC and SC AA 5182 aluminum alloys during rolling. The texture volume fractions were computed by a new method, in which the Euler space representing all possible crystallographic orientations in rolling was subdivided into the cube, r-cube, Goss, r-Goss, β fiber, and random orientation regions based on the slip pattern combined with the characteristics of microstructure and texture. Empirical formulae of the texture volume fractions and true strain were constructed to predict the texture of cold rolled DC and SC AA 5182 aluminum alloys. The results show that the processing method (DC vs. SC) strongly affects the texture after annealing at 454 °C and the texture evolution during the subsequent rolling.

A study of twinning in zirconium using neutron diffraction and polycrystalline modeling

An experimental study using neutron diffraction quantified the evolution of twinning in pure clockrolled zirconium that was subsequently deformed under uniaxial compression. The clock rolling introduced an initial texture of approximately 5 times random, and the compression specimens were cut with their loading axes nearly parallel to the predominant c-axes direction. Seven specimens deformed to strains between −2 and −17 pct and an undeformed specimen (0 pct strain) were examined. The deformation was performed at an applied strain rate of 0.001/s at 77 K. Twin volume fractions were estimated from diffraction data. Changes in texture and twin volume fractions were compared to predictions from a visco-plastic self-consistent (VPSC) polycrystal model, which described both slip and twinning. This work demonstrates the feasibility of using neutron diffraction to track the evolution of twinning. These results help benchmark the polycrystalline model, validate the description of twinning, and potentially lead to a better understanding of its role in hardening.

Phase Relationships and Phase Formation in the System BaF2-BaO-Y2O3-CuOx-H2O

ABSTRACTThe interplay of melting equilibria and reaction kinetics is important during formation of the Ba2YCu3O6+x (Y-213) phase from starting materials in the quaternary reciprocal system Ba,Y,Cu//O,F. For experimental investigation of the process we used a combination of differential thermal analysis (DTA) for study of melting equilibria, and in-situ high-temperature x-ray diffraction (HTXRD) for study of the phase formation and reaction kinetics. DTA investigation of compositions spaced along compositional vectors extending from the oxide end to the fluoride end of the reciprocal system have given evidence of low melting liquids (∼600 °C) near the fluorine-rich end. Work is continuing to determine whether similar thermal events observed in the interior of the system also indicate low temperature liquids, and on the extent to which low-melting liquids could be involved in Y-213 phase formation. HTXRD investigations have been initiated on the conversion of 0.3 μm and 1.0 μm thick BaF2-Y-Cu precursor films to Y-213 in the presence of water vapor. Preliminary results indicated that the thickness of film has a strong influence on the texture of the Y-213 film: a 0.3 μm film showed mainly (001) texture, whereas a 1.0 μm film showed a greater volume fraction of (h00) texture. While the HTXRD method cannot directly reveal the presence of liquid, we are working to combine DTA and HTXRD data for a unified picture of Y-213 phase formation during the “BaF2 ex-situ” process for coated-conductor fabrication.

“in-situ” neutron diffraction study of the cube crystallographic texture development in Fe53%-Ni alloy during recrystallization

Laboratoire de physico-chimie de l’e´tat solide, U.M.R. 8648, Baˆt. 410, 91405 Orsay, France(Received February 24, 2000)(Accepted in revised form April 3, 2000)Keywords: Texture; Recrystallization and recovery; Iron-nickel alloyIntroductionMany investigations have been carried out on the recrystallization crystallographic texture of rolledmetallic materials. However, the formation mechanism of the recrystallized grains with a preferredorientation has not been clarified yet. In particular, in the case of fcc metals and alloys from mediumto high stacking fault energy such as FeNi alloys, the cube texture {100},001. development duringrecrystallization is not clearly understood in spite of intensive studies. Several mechanisms have beenproposed to explain this phenomenon and two main alternative theories are generally proposed: orientednucleation (1) and oriented growth (2). Nevertheless, these theories are not satisfactory to explain fullythe cube texture development during recrystallization and in particular, they can not give any infor-mation on the time scale of the phenomenon. In this purpose, “in situ” texture measurements duringrecrystallization have been performed.The Fe53%-Ni alloy is widely used as soft magnetic sheet materials. After high reduction, cold rolledtexture is characterized by three main components considered as a typical copper-type texture (3): the“brass” {110} ,112. (B), the “aluminium” {123} ,634. (S) and the “copper” {112} ,111. (C)components. After annealing, a typical strong cube texture {100},001. development is observed.The aim of this paper is to study the crystallographic texture evolution of the Fe-53%Ni alloy duringannealing and the influence of the annealing temperature on the recrystallization kinetics. Then, the useof neutron diffraction is particularly requisite on the one hand to achieve good statistic measurement,even for small texture volume fraction and, on the other hand to use complex sample surroundings, asa furnace, necessary for the “in-situ” recrystallization study.Experimental ProcedureAfter hot rolling, the Fe-53%Ni alloy was cold rolled with a 95% reduction, until a final thickness sheetof about 0.2 mm. So in order to perform “in-situ” texture measurements by neutron diffraction, a pileup of 50 pieces (1cm 3 1cm) is realized in a vanadium (almost “transparent” for neutron diffraction)cubic container (1cm

Preparation and evaluation of cube texture Ni substrate for YBCO-coated superconductor

The cube-textured Ni tapes were prepared by deformation rolling at room temperature and followed by recrystallization annealing at 950–1000°C for 5–10 h in a high vacuum under 10 −4 Pa. The formation and evolution of rolling and recrystallization textures have been investigated by X-ray pole figures and orientation distribution function (ODF). The results show that the C {112}〈1117〉 and S {123}〈634〉 orientation densities along β-fiber in rolling textures of Ni substrate increase with increasing reductions; and the cube texture volume fraction index increases, ϕ scan FWHM decreases with increasing heat-treatment temperatures for samples deformed with 95% reduction. In the recrystallization textures, the cube texture component in ODF ϕ=0 section deviates from regular positions (0° 0° 0°) in the range of 12–13° at lower heat-treatment temperature. By increasing the heat-treatment temperature up to 1000°C, the deviation from regular position decreases, and sharp cube texture is formed.

Calculation of Texture Volume Fractions by Integration andGaussian Fitting

The concept of texture volume fractions has proved useful in the assessment of the orientation distributions of polycrystalline samples. Unfortunately, there is more than one method of calculating volume fractions, and the different techniques may give rather different answers. The three most commonly used methods appear to be calculation from the coefficients of the harmonic function, integration over a selected portion of an orientation distribution function (ODF), or decomposition of an ODF into component Gaussian ideal textures by a least squares fitting. The integration and Gaussian fitting methods are examined further here. In particular, the nature of the errors or differences arising from the method of integration or fitting chosen, the differing interpretations of the shape and ‘spread’ of the ideal texture, and the effect of neglecting texture components lying outside of the H0 subspace are considered. Integration of a volume enclosed by one or more cylinders defined in Eulerian space seems the most robust technique. It is usually, but not always, acceptable to neglect the effect of texture components lying outside of H0. However, it is vital that the ‘spread’ of the ideal texture component be precisely defined, and the texture volume fraction is very sensitive to the magnitude of the spread as well as to the geometric shape assumed for it.