Issue 78

A. A. Frantsuzov et alii, Fracture and Structural Integrity, 78 (2026) 474-488; DOI: 10.3221/IGF-ESIS.78.27

Figure 12: PAGS distributions obtained by two operators using the lineal intercept method and by manual diagonal measurements.

Figure 13: Comparison of PAGS distributions obtained by the manual diagonal method and by EBSD reconstruction.

For the SEM EBSD map acquired at ×1000 over an area of 125×100 μ m, approximately 300 reconstructed PAGs were indexed. In comparison, for an optical micrograph acquired at the same magnification over an area of 115×85 μ m, the operator confidently measured only approximately 30 grains using the diagonal method and approximately 100 grain boundary intersections using the lineal intercept method. Although the optical field of view was only about 15 % smaller than the EBSD map area, the number of measured PAGs was lower by approximately 90 % for the diagonal method and by approximately 33 % for the lineal intercept method. This difference explains why the manually obtained distributions in Figure 13 are steeper than the distributions obtained by EBSD reconstruction. Similarly, the smaller field of view at higher EBSD magnification contributes to the steeper distributions observed in Figure 8. The final manual comparison was performed using ASTM E112 standard comparison plates on the same optical images. Visual comparison gave a grain size number of 10.0, corresponding to an average grain diameter of approximately 11.2 μ m according to the standard table. The average grain sizes obtained by the different methods are summarized in Table 3. The EBSD reconstruction results show a decrease in the average grain diameter with increasing magnification. However, at ×500, which corresponds to the magnification used for the manual measurements, the EBSD reconstruction and manual methods show good agreement. The difference between the two operators in the lineal intercept method reached approximately 2 μ m in average grain size, while this method also gave the highest standard deviation, approximately 4 μ m. This indicates that the lineal intercept method is strongly affected by poorly defined PAG boundaries. The higher grain size obtained by comparison with ASTM

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