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Super fast 3D tomographic images
August 29, 2018
Source: ASM International
Helmholtz-Zentrum Berlin announces that the fastest 3D tomographic images to date have now been achieved by the BESSY II x-ray source. This speed can be beneficial with metallic foams where fast sensing capability can capture a series of microstructures as the foaming process takes place.
Dr. Francisco Garcia-Moreno and his team at Helmholtz-Zentrum designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends on the highest precision: Any tumbling around the rotation axis or even minimal deviations in the rotation speed would prevent the reliable calculation of the 3D tomography. While commercially available solutions costing several hundred thousand euros allow up to 20 tomographic images per second, the Berlin physicists were able to develop a significantly cheaper solution that is even faster. In addition, Garcia-Moreno and his colleague Dr. Catalina Jimenez had already developed specialized optics for the fast CMOS camera during the preliminary stages of this work that allows even for simultaneous diffraction. This makes it possible to record approximately 2000 projections per second, from which a total of 25 three-dimensional tomographic images can be created.
As a first example, the team investigated granules of aluminum alloys that become a metallic foam when heated. To do this, they mounted a powerful infrared lamp above the metal granulate to heat the sample to about 650°C. A complete 3D tomographic image with spatial resolution of 2.5 µm (pixel size) was generated every 40 ms. The nearly 400 tomographic 3D images now allow detailed, time-resolved analysis of the process as it occurred.
“We wanted to develop a better understanding of how pores form in the grains—whether they also reach the granule surfaces and to what extent this process varies in different granules,” explains Garcia-Moreno. It is a question of practical relevance that is also of interest to industry. Granules of metallic compounds might fill complicated shapes better while foaming than foams manufactured from a block of metal. However, the molded part will only be able to withstand stress if the grains also bond closely with one another during foaming. With the ultra-fast 3D tomography developed at BESSY II, this can now be observed very precisely.
Image – Granules of aluminum (grey) become a metallic foam when heated. The tomographies document the evolution of pores with time. Courtesy of HZB.
For more information:
Materials Properties and Performance | Mechanical Properties
Materials Testing and Evaluation | Materials Characterization
Materials Testing and Evaluation | Metallography and Microstructures