AFM is useful for analyzing nanoparticles. See here an example: http://www.nanoscalereslett.com/content/pdf/1556-276X-6-514.pdf

However your question needs to be more precise: is it alloy or composite? Alloy and composite are two different material classifications.

Thanks sir for reply. I added Al2O3 nano particle (50 nm ) in Al6061 alloy by casting method.Is AFM method is suitable for examine the nao particle distribution in Al6061 alloy?

It would not be too productive using a metallic polished sample  for finding nanoparticles in it. To reveal a nanopaticle you have to etch the sample so that AFM could be used either in contact or half-contact tapping mode. At the same time the maximum field of view of AFM instruments is hundreds by hundreds of micrometer so finding a nanoparticle there could be too tedious. There are some specific AFM modes which alloy detecting particles by the difference in Young modulus and such an approach would be most useful since it does not require etching. However, TEM or SEM would be most useful methods.

Hi Neeraj,

It would be more appropriate to use TEM to observe nanoparticles and its distribution in your composite samples, AFM/SEM may not be so helpful.

Yes, I agree with Praveennath Koppad. TEM is the best technique for observing nanoparticle distribution in a matrix. However, the sample preparation for TEM is critical. You may try it once.