= Solution
Use the line fraction occupied by the tall narrow ridges as an estimate of <cementite> <volume fraction>, assuming the line is representative and its etched height classification identifies the phases correctly. \b[The displayed profile gives roughly $17\,\mathrm{vol\%}$ <cementite> and $83\,\mathrm{vol\%}$ <ferrite>.]
An operational measurement at a height threshold near $75\,\mathrm{nm}$ gives four ridge widths totaling about $0.88\,\mathrm{\mu m}$ over a profile about $5.3\,\mathrm{\mu m}$ long:
$$
\boxed{f_{\rm cem}\simeq\frac{\sum_jw_j}{L}\simeq\frac{0.88}{5.3}\simeq0.17,
\qquad f_\alpha\simeq0.83.}
$$
Changing the threshold over a reasonable part of the high ridges gives roughly $16$–$18\%$, so this is an image-based estimate, not an exact phase analysis. The occasional low protrusions should not all be counted as full <cementite> lamellae merely because they are above a noisy baseline. The reference line and threshold convention must be stated.
Back to article page
