Broad ion beam serial section tomography

• Published in: Ultramicroscopy 2017-01, Vol.172, p.52-64
• Main Authors: Winiarski, B., Gholinia, A., Mingard, K., Gee, M., Thompson, G.E., Withers, P.J.
• Format: Article
• Language: English
• Subjects: 3D electron back scattered diffraction; Automation; Cermet; Computed tomography (CT); Data acquisition; Focused ion beam (FIB); Indexing; Ion beam polishing; Ion beams; Manuals; Quantitative analysis; Scanning electron microscopy; Serials; Tomography
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2016.10.014

Here we examine the potential of serial Broad Ion Beam (BIB) Ar+ ion polishing as an advanced serial section tomography (SST) technique for destructive 3D material characterisation for collecting data from volumes with lateral dimensions significantly greater than 100µm and potentially over millimetre sized areas. Further, the associated low level of damage introduced makes BIB milling very well suited to 3D EBSD acquisition with very high indexing rates. Block face serial sectioning data registration schemes usually assume that the data comprises a series of parallel, planar slices. We quantify the variations in slice thickness and parallelity which can arise when using BIB systems comparing Gatan PECS and Ilion BIB systems for large volume serial sectioning and 3D-EBSD data acquisition. As a test case we obtain 3D morphologies and grain orientations for both phases of a WC-11%wt. Co hardmetal. In our case we have carried out the data acquisition through the manual transfer of the sample between SEM and BIB which is a very slow process (1–2 slice per day), however forthcoming automated procedures will markedly speed up the process. We show that irrespective of the sectioning method raw large area 2D-EBSD maps are affected by distortions and artefacts which affect 3D-EBSD such that quantitative analyses and visualisation can give misleading and erroneous results. Addressing and correcting these issues will offer real benefits when large area (millimetre sized) automated serial section BIBS is developed. •In this work we examine how microstructures can be reconstructed in three-dimensions (3D) by serial argon broad ion beam (BIB) milling, enabling much larger volumes (>250×250×100µm3) to be acquired than by serial section focused ion beam-scanning electron microscopy (FIB-SEM).•The associated low level of damage introduced makes BIB milling very well suited to 3D-EBSD acquisition with very high indexing rates.•We explore and compare for the first time the application of Broad Ion Beams (BIBs) using the Gatan PECS and Ilion systems for large volume serial sectioning and 3D-EBSD data acquisition.•Volumetric data registration schemes usually assume that the data comprises a series of parallel, planar slices. We quantify the variations in slice thickness and parallelity which can arise when using BIB systems.•Raw 3D-EBSD data is affected by distortions and artefacts arising from serial sectioning such that quantitative analyses and visualisation can give mislea