Measurement of macrotexture by automated crystal orientation mapping: An alternative to X-ray diffraction

Automated crystal orientation mapping (ACOM) with digital beam scan in the SEM enables crystal orientation mapping and quantitative texture analysis on large specimen areas of half a square centimetre wide or more, without sacrificing accuracy of orientation measurement or spatial resolution, provided that program facilities for dynamic focusing of the beam, dynamic system calibration, and automatic flat fielding for background correction are available. At present, the speed of ACOM exceeds 25 000 orientations per hour with cubic and hexagonal crystal symmetry. The orientation density function has been calculated using the data from ACOM measurement by series expansion under the assumption of triclinic sample symmetry and various spreads of the Gaussian function. ACOM competes well in speed and in results with X-ray diffraction, but is a more universal instrument owing to the additional facilities of SEM. Grain statistics are similar with both techniques since they depend on the ratio of average grain size to measured area. The advantages and limitations of macrotexture determination by ACOM are discussed.