Electron Backscatter Diffraction
ASTM grain size is a property written into many specifications for metals, with finer grain sizes generally indicating better mechanical properties such as formability. While measuring certain materials for such properties can be difficult, electron backscatter diffraction can provide precise determinations as well as give information on grain size distribution and statistics.
A new ASTM International standard covers electron backscatter diffraction. E2627, Practice for Determining Average Grain Size Using Electron Backscatter Diffraction (EBSD) in Fully Recrystallized Polycrystalline Materials, was developed by Subcommittee E04.11 on X-Ray and Electron Metallography, part of Committee E04 on Metallography.
“The standard will be most useful to metals users and producers, particularly those whose materials prove difficult for traditional techniques,” says John Friel, a retired assistant professor of geology, Temple University, and chairman of E04.11. “Ceramics industries could also use EBSD because their materials are difficult to etch and do not electropolish.”
Friel also notes that, because EBSD is a direct measurement of grain size, E2627 can be used to referee disputed measurements made through other techniques.
“EBSD can be used on any crystalline material; thus it is often used for structural and texture studies in geology and materials science,” says Friel. “With E2627, we have adapted the technology and standardized the method of data acquisition and reporting to extract more information from the traditional, yet ongoing, need for grain size measurement.”
Technical Information: John Friel, Temple University, Philadelphia, Pa.
ASTM Staff: Kathleen McClung