The ability to use CrossCourt4 for comparing strain measurements between successive scans has been made possible by saving the reference patterns obtained in the first scan and using them in repeat scans. On analysis this is not a straightforward procedure in HR EBSD and BLGVantage and its associated scientists have spent considerable time studying and evolving a practical solution.
It is essential in such experiments that the relative positions of the respective diffraction pattern centres in each scan are known to sub pixel accuracy. This is currently only possible using the patented BLG Vantage shadow casting procedure. The entire implementation of this process has been seamlessly incorporated into an extension of the CrossCourt 4 software and requires the attachment of a fixed aperture in front of the EBSD detector’s phosphor screen.
Fig. 1 Example of the BLG Nose Cone EBSD detector extension
Note that as HREBSD is sensitive to a beam movement of 3µm or less, even in-situ experiments will need pattern centre tracking as drift of several microns is almost certainly going to occur over the timescale of the experiment. Details of the attachment and ease of adoption for particular EBSD systems can be obtained by contacting BLG Vantage directly.
Examples of when sequential dataset collection is useful include:-
- a specimen may have been removed from the microscope for thermal treatment between the scans
- in-situ tensile straining experiments may have been carried out in which scans before and after yielding are required.