0.1.1 Surface preparation

    • Grinding: P-320-400-600-1200-2500-4000
    • Diamond polishing: 7/8 µm, 3 µm, 1 µm
    • Electropolishing: Ortho phosphor acid
    • OP-S: Struers “OP-S Non-Dry” + ammonia + hydrogen peroxide
    • Etching:  5g ferric chloride + 10ml conc. hydrochloric acid + 100 ml de-ionised water
    Tabell 1 Tabell 1

    0.1.2 SEM specifications

    • SEM:   Zeiss GeminiSEM 450
    • EDS:   Oxford instruments Ultim Max 100 mm2
    • EBSD:   Oxford instruments Synergy
    • Software packages:   AZTEC, AZTEC Crystal

    0.1.3 Material conditions

    • Extruded bars

    0.1.4 EBSD explained

    Electron Back-Scattered Diffraction, EBSD, is a diffraction based SEM technique where phases and crystal orientations are analysed. EBSD can analyse any known crystalline material; metals, ceramics, oxides, rocks, ice. Metals are generally easy to analyse due to the good electric conductivity and due to generally easy crystallographic symmetries (FCC, BCC, HCP).  The phase need to be known, a description of the crystal need to be given to the analysis software.

    EBSD mapping builds up microstructures by analysis of phase and crystallographic orientations in grid. In each pixel additional information on diffraction pattern quality and the fit to the simulated pattern. Misorientations between pixels can be used in different way, grain boundaries and phase boundaries are examples of this. A grain boundary is usually defined as a misorientation > 15deg. Low angle boundaries (built up from dislocations) are commonly defined as misorientation between 1 to 2 deg. and 15 deg. 1 to 2 deg. misorientation is used as a threshold to avoid analysis noise and surface damages from preparation.

    IPF colouring: Crystallographic directions are coloured according to directions, by directions it is understood that the normal to the close-packed plane is parallel to the given direction, X, Y or Z. In a rolled plate specimen directions are usually aligned so that X=RD, Y=ND and Z=TD. In extruded bars it is convenient to align ED with X. Then Y and Z are both equal to TD due to the symmetry. The colouring key is from Oxford instruments EBSD software AZTEC.