For getting the JCPDS card number of your compound you select all the elements present in your alloy or compound material and then find the possible combination using X'pert High score software. Most probably more than one combinations you can find and match them from your XRD data carefully.
The resulting XRD result for the resulting material is considered as a composite with the possibility of a chemical union between them. So also as single phases of each element. The analysis may also contain borderline phases. To analyze correctly, it is good to know the chime composition of the two alloys.
If you have a chemical analysis and the data from the XRD analysis in the *.DAT file I can read the diagram as phases.
Here is a method to compare the XRD data with JCPDS data, it may helpful to you, https://www.researchgate.net/publication/339363196_Match_XRD_data_with_JCPDS-_A_method_2020/stats