Qualitative determination of retained ausenite content in the heat treated steels is possible by X-ray diffraction technique. One of the basic approach is by comparing integrated intensities.
The expression for the intensity diffracted by a single phase powder specimen in a diffractometer is given by:
Above equation can be rewritten as:
K2 depends only on incident beam, but not on crysal structure.
R depends only on crystal structure, but not on surrounding phase.
depends on both crystal structure and surrounding phase.
Thus for Austenite and Martensite above euation becomes:
From these two equations:
In this equation we have to caluclate to evoluate reatined austenite.
and are the integrated intensities for each of the diffraction line (area unde the curve after background substraction).
By considering , we can find out the actual amount of each phase. By cosidering several pairs of austenite and matensite lines, we can obtain several values of retained austenite content.