Grain size and phase analysis of microstructure images
A polished and etched metal specimen is imaged field by field on the microscope stage. In every field the grain boundaries are segmented, the mean grain size is computed by the intercept method and the phase fraction by a grey-level threshold; coarse grains, pores and inclusions are marked.
Grain size, distribution histogram and phase fraction per field are written to the report; an out-of-limit field is flagged in the specimen record and the display shows the image with the boundaries drawn.
- 01 Field selection
- 02 Acquire
- 03 Segmentation
- 04 Measure
- 05 Decide
The motorised stage moves the specimen to the next field.
- Mean grain size
- —
- Second-phase fraction
- —
- Inclusions
- —
Scenes are illustrative simulations; they are not customer references or performance guarantees.
Need
Etching contrast varies from specimen to specimen; grain boundaries are faint in places, while scratches and inclusions look like boundaries. Manual counting is slow and operator-dependent; consistency between fields is required.
Solution approach
A motorised stage brings the specimen to predefined fields and the camera images each field with the same illumination and focus. Boundary lines are segmented by local contrast and closed; the grain-size distribution follows from the area and intercept methods, the phase fraction from a grey-level threshold. Pores and inclusions are separated from grains by shape and darkness.
Process steps
- 01
Field selection
The motorised stage moves the specimen to the next field.
- 02
Acquire
The field is imaged under coaxial illumination.
- 03
Segmentation
Grain boundaries are found and closed; pores and inclusions are separated.
- 04
Measure
Grain-size distribution and phase fraction are computed.
- 05
Decide
Mean grain size and phase fraction are compared with the limits.
Related applications
Let us assess your application together
We test your sample in our laboratory and report on resolution, optics and lighting selection.