IPF a OIM schma A Grain Boundary Map

IPF a OIM - schéma

A Grain Boundary Map can be generated by comparing the orientation between each pair of neighboring points in an OIM scan. A line is drawn separating a pair of points if the difference in orientation between the points exceeds a given tolerance angle. An Orientation Map is generated by shading each point in the OIM scan according to some parameter reflecting the orientation at each point. Both of these maps are shown overlaid on the digital micrograph from the SEM.

• • Grain size distribution determination Methods – Intersection method • vertical • horizontal • #. of lines – Area detection method • 4 neighbors • 8 neighbors Setting of the maximal misorientation Frequencies of lengths (or areas) • creation of histogram • size of the bin! • fitting with “chosen” function

Grain or sub-grain? • SE vs. EBSD - Different results SE pictures does not show internal structure of grains – we can see phase boundaries (conglomerates of grains) EBSD determines orientation of each point – we can really see the crystallites! (Ti, W)(C, N) Definition of the “grain” and “crystallite” WC (Ti, W)(C, N) grain scanning

SE x EBSD Bigger grains correspond to the (Ti, W)(C, N) T 08 T 80 Completely different results obtained from SE and EBSD!!! SE does not see crystallites, but conglomerates of crystallites d. SE > d. EBSD

CBED x EBSD

Algoritmus vyhodnocování EBSD Image quality Orientace hkl , 1, 2 Mříž. parametry Textura, Pólové obrazce OIM Misorientace Velikost zrna Rotace mříže Subzrna Kvalitativně r Hustota dislokací Fázová analýza

Srovnání různých experimentálních metod studia mikrostruktury Synchrotron Radiation (H. F. Poulson & D. Juul-Jensen) Low Spatial Resolution (5 mm), moderate angular resolution (1 -2°), Good statistics, 3 -d information, difficult mathematical reconstruction, poor availability Polarized Light (R. Heilbronner ) Not very quantitative, inexpensive, good accessibility, 2 -d, limited materials TEM Diffraction (Kikuchi patterns, Spot patterns, CBED) High spatial resolution, good accuracy, extremely limited area, difficult sample preparation, as of yet - limited automation, some 3 -d information, poor statistics Electron Channeling Poor spatial resolution (5 -10 mm), moderate accuracy (0. 5°), 2 -d, no automation so poor statistics. Kossel X-Ray Diffraction Poor spatial resolution (10 mm), good accuracy (0. 1°), 2 -d, limited materials, no automation so poor statistics. Electron Backscatter Diffraction Good spatial resolution (~20 nm), good angular resolution (~1°), reasonable statistics with automation, good availability, 2 -d

Orientation based maps – IPF map (2 D), Euler Angle map, Component maps Misorientation Based Maps – local misorientation (strain)… Non-Orientation Scalar maps – IQ, CI, fit, Other detectors (FSD, SED, X-Ray), phase… Property Maps – Taylor or Schmid Factor, Elastic Modulus Grain Based Maps – size, shape, avg IQ, orientation spread… Misorientation charts – local misorientation (strain)… Non-Orientation Scalar chart – IQ, CI, fit, Other detectors (FSD, SED, X-Ray), phase… Property chart – Taylor or Schmid Factor, Elastic Modulus Grain Based Charts – size, shape, avg IQ, orientation spread…

EBSD je nástroj na studium: Plastické deformace (50 - 60%); - Zotavení a polygonizace; - Rekrystalizace; - Procesy tání a tuhnutí; - Fázové transformace; - Fázová analýza (kvantifikace); - Historie struktury; - Pólové obrazce a anizotropie, atd. -