High spatial resolution EBSD mapping using an eFlash XS detector on a FE-SEM

The spatial resolution of EBSD technique is influenced by multiple factors with the most important being: local average Z number of the sample, accelerating voltage and probe size of the electron beam. Lowering the last two leads to significant gains in spatial resolution but also results in a strong decrease in signal yield thus affecting the data quality and/or the acquisition speed. W-SEMs represent the best value-for-money solution, for routine EBSD measurements on materials with grain diameters larger than 1 μm. When characterizing microstructures containing features smaller than 1 μm and especially for those smaller than 500 nm, FE-SEMs represent the best/only practical choice due to their ability of delivering great ratios of probe current vs. probe size.

Fig. 1 Pattern Quality Map (PQM) of a +2M pixels EBSD dataset acquired from an Alpha-Beta Ti-alloy sample in steps of 75 nm using eFlash XS EBSD detector mounted on a TESCAN Mira 4. Zoom-in view of highlighted area in PQM map depicting very fine features (upper-right) and grey level distribution histogram (bottom-right). Dark grey pixels represent areas of reduced crystallinity, e.g. grain boundaries.
Fig. 2: Phase distribution map with Alpha-Ti phase in green and Beta-Titanium in red. Phase and non-indexed points fractions are given in the legend.
Fig. 3: Crystal Orientation Map of Ti-alloy sample using standard coloring scheme for Alpha and Beta phases to depict orientation of simple crystallographic directions with respect to the normal to the sample surface.
Fig. 4: Crystal Orientation Map subset showing Beta phase grains and their orientations with respect to the normal to the sample surface.
Fig. 5: Reconstructed grains map showing, in random colors, Alpha and Beta Titanium grains detected using a 5 degrees misorientation criterion and a minimum 10 pixels size criterion.
Fig. 6: Grain size distribution histogram for Alpha and Beta Titanium phases. Total number of grains, area weighted mean equivalent diameter as well as the median diameter size are also given. Please note that all grains touching the map’s edge were not included in statistics and histogram.
Fig. 7: Diameter size distribution histogram and statistics of Alpha Titanium grains.
Fig. 8: Diameter size distribution histogram and statistics of Beta Titanium grains.
Fig. 9: Grain Average Misorientation (GAM) map of Alpha-Beta Ti-alloy sample with corresponding legend. The map indicates that certain regions/grains in the sample are in a deformed state (light blue – green – orange pixels) while others are fully recrystallized (blue pixels).
Fig. 10: Subset of GAM map representing ~34% of the entire map and displaying the grains/regions in a deformed (plastically) state.