If the alloy is an homogeneous phase (as you stated) and althought if the metals A and B have the same crystal structure, the alloy must have a different diffraction pattern with respect to the elements A and B according to their respective phase diagram.

Thanks for the response.. Could you share some journal or material regarding the same.

Adhidesh! Why don't you post the 3 diffractograms for "nano particles of metal A and metal B. Also of their mixture of composition"? This will make your discussion more interesting and the "expert" suggestions more focused as well as more meaningful :-)

Pb-Bi Phase Diagram: http://www.himikatus.ru/art/phase-diagr1/Bi-Pb.gif

BTW you may also increase the number of topics up top to as many as 15. Please look at the following RG question for additional relevant topics to post your query in. This will significantly enhance the participation rate and hence both the quality and quantity of responses. Adding links and references, as shown below, will help you a great deal!

Good basic question with volumes of references and examples available in literature!

https://www.researchgate.net/post/What_is_the_best_way_to_interpret_REAL_TIME_3D_X_Y_Omega_2Theta_reciprocal_space_relative_intensity_data_from_HRXRD_rocking_curve_analyses

https://www.google.com/?gws_rd=ssl#q=pb-bi+phase+diagram

when u mix the both metals in different const and make a new alloy the X-Ray pattern for the alloy must change from parent compound the simple way to find it is you can get multi peaks one peak overlap with other  for e.g. see the pic

Besides, if your nanoparticles are below 10 nm size the amorphous layer on the surface of your nanoparticles will reach a large proportion of your material. The peaks will become broader and there might be a high background due to amorphous condition a low angles. I yours is just a mixture and not a compound the peaks will tend to overlap. If they become a unique phase the peaks will broaden. Metalic species are easy to predict by watching the phase diagrams. No relationship with the nano character of the alloy itself except for the peak shape and background.

Dear Adhidesh Kumawat 

1. According to the Hume-Rothery rules Pb and Bi do not form a continuous sold solution (see phase diagram Pb-Bi).

2. According to the phase diagram Pb-Bi, at room temperature the alpha-phase is a solid solution with an an fcc-lattice and containing substitutional dissolved Bi atoms up to about 18 at % Bi. For this composition range it can be expected Vegard's rule to be valid, i.e. a linear relation between the fcc-lattice parameter and Bi-content in at%.

3. At room temperature, the Pb-Bi phase diagram shows again a monophase solid solution for the composition range between approximately 28 and 38 at %; currently I cannot inform you about the lattice type of this solid solution; however it can be stated that this sold solution for the indicated restricted composition range will follow Vegard's rule.

4. For other composition ranges you will encounter two phases with each different lattices at room temperature.

5. Note that size effects may have an effect on XRD line broadening. 

how to interpret alloy has formed by just looking XRD graph?