Papers by Keyword: ODF Analysis

Abstract: Ultrafine-grained (UFG) commercial pure (CP, grade 3) Ti was produced by two-step severe plastic deformation (eight-pass equal channel angular extrusion (ECAE) at 400 °C and cold rolling (CR) at room temperature (RT)). The crystallographic texture in UFG CP-Ti and coarse-grained (CG) CP-Ti (annealed) after CR at RT are studied by orientation distribution function (ODF) analysis, based on X-ray diffraction. The relationship between the texture components and mechanical properties of UFG CP-Ti after two-step severe plastic deformation (SPD) has been discussed. ODF analysis shows that the main texture components in UFG Ti after CR at RT are (011—5)[11— 01], (011—5)[22—01], (0001)[1—3—43] and (011—3)[21—1—1], while the texture components of (011—3)[1—101—] and (011— 3)[2— 201] appear in CG CP-Ti after CR at RT. The values of Schmid factor for prismatic- slip systems are larger than that for basal slip systems and other slip systems, which is more in favor of the activation of prismatic-. In addition, higher strength of texture in favor of the activation of prismatic- in UFG CP-Ti improves its plasticity.

Abstract: One of the design goals of the neutron time-of-flight (TOF) diffractometer HIPPO (HIgh Pressure - Preferred Orientation) at LANSCE (Los Alamos Neutron Science Center) was efficient quantitative texture analysis. In this paper, the effects of the HIPPO detector geometry and layout on texture analysis, particularly the shape and dimensions of the detector panels, are investigated. An aluminum sample with a strong and asymmetric texture was used to determine the methodological limitations of various methods of quantitative texture analysis. Several algorithms for extracting the orientation distribution function (ODF) from the TOF-spectra are compared: discrete orientations at arbitrary positions, harmonic method in Rietveld codes (MAUD and GSAS) and discrete methods in MAUD. All methods provide a similar representation of the main texture component, but discrete methods have a fundamental advantage over harmonic methods in characterizing regions of the ODF with low orientation densities. For HIPPO data of the present sample, harmonic expansions beyond lmax= 12 introduce subsidiary maxima and minima, which are consistently identified as artifacts. The results of our analysis establishes HIPPO as an efficient instrument to quantitatively determine preferred orientations in relatively short measuring times, if the texture features are not exceedingly sharp (full-width at half-maximum (FWHM) in the ODF > 20-30°).