Characterization of Dislocations Found in an Array at a Mixed Character Small Angle Boundary of a Cross Rolled and Annealed Aluminium Sample

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Formation of a Small-Angle Boundary During Annealing of a Cross Rolled Aluminium Sample

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Evolution of a Small Angle Boundary from a Perfect Lattice During Annealing of a Cross Rolled Aluminium Sample

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Quantitative texture analysis with the HIPPO neutron TOF diffractometer

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 in detail. An equal-channel angular-pressed (ECAP) aluminium sample with a strong 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 methods in Rietveld codes (MAUD and GSAS) and discrete methods in MAUD. Because of the detector geometry, the sharpest texture peaks that can be represented are 12–15° in width, resulting in an optimal texture resolution of 25–30°. Due to the limited resolution and incomplete pole-figure coverage, harmonic expansions beyond L = 12 (where L is the maximum degree of the harmonic expansion) introduce subsidiary oscillations, which are consistently identified as artifacts. Only discrete methods provide a quantitative representation of the texture. Harmonic methods are adequate for a qualitative description of the main texture component. The results of the analysis establish HIPPO as an efficient instrument to determine preferred orientations in relatively short measuring times.