November_December_2021_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 1 3 1 that combines (S)TEM imaging with a Super-X EDS system that offers four EDS detectors to obtain the composition of precipitates. To accommodate this new instrument, OCAS built a new micros- copy lab in the basement of its head- quarters in Zelzate, Belgium, to ensure temperature fluctuations and vibra- tions are minimized. Using the Talos, technicians take a low-magnification TEM image to assess the distribution of the precipitates and determine the ho- mogeneity of the distribution (Fig. 1). After the homogeneity is evalu- ated for several of the hexagonal grid holes on a carbon replica, one grid hole is selected to represent the distribu- tion across the sample for precipitate analysis, and 64 dark field STEM im- ages are automatically launched at a user-specified location by Maps soft- ware (Fig. 2). These images are then stitched together to form the over- view map of the selected hexagonal hole. The total area for the stitching is 117 x 117 µm, and the process takes approximately 2 minutes for manual setup and 10 minutes for automatic im- aging and stitching. With an overview map, techni- cians can see all precipitates across a defined area, including their morpholo- gy, size, and distribution. They can also zoom in to 8 nm per pixel and view pre- cipitates in more detail while tracking how each examined area corresponds to its position within the larger over- view map. When more information is needed for a region of interest on the overview map, a double-click on the re- gion in Maps software leads directly to the spot, where a higher magnification STEM imaging or EDS analysis can then be launched. The overview image serves as a roadmap, guiding operators to the pre- cipitates they need to analyze in great- er detail and more closely observe the parameters that are either enhancing or negatively impacting steel quality. In some cases, all the information that’s needed can be obtained in the few min- utes it takes to produce an overview map; no further analysis is required. AUTOMATED EDS IMAGES For full EDS information across a defined area, operators can also run automated EDS maps to deter- mine the chemical makeup of pre- Fig. 1 — Left: The low-magnification TEM image is taken to assess the homogeneity of precipitate distribution on a large scale. Right: Example of 3 mm TEM grid with carbon replica film applied. Fig. 2 — Left: An 8 x 8 grid is ready to collect 64 dark-field STEM images in the center of this randomly chosen grid hole. Right: The overview image has been completed with 8 nm pixel resolution. Fig. 3 — One hundred titanium EDS maps are collected in this 10 x 10 grid with 2.837 nm pixel size in an overnight run. Fig. 4 — Left: One titanium EDS map. Right: The precipitates have been segmented and labeled by Avizo2D.