1. X-ray tube targets and power conditions
The power conditions depend on the X-ray tube as the target material and focus type. Although Cu targets are widely used for diffraction, it is not recommended to use Cu targets for residual austenite analysis because of the strong fluorescence of iron-based materials.
ASTM notes that the recommended choice is Cr or Mo, depending on whether it is necessary to obtain better resolution (Cr) or whether it is necessary to collect as many peaks as possible (Mo) to minimize sample problems. In addition, the higher radiation energy of the Mo target can also minimize the absorption effect, resulting in a higher count rate. Therefore, Mo target is preferred for residual austenite test.
2. Comparison of actual test between Mo target and Cr target
For XRD measurements of residual austenite, any radiation target that records at least 2 alpha iron peaks and 2 gamma iron peaks can be used.
As shown in the figure below, the use of Mo targets has other advantages over Cr targets, such as the test error of Cr targets is greater than that of Mo targets.
Powder XRD