Abstract: Nanocrystalline Fe-Cu alloy powders were prepared by mechanical alloying.The solid phase transformation,microstructure and grain size variation of milled powder mixtures during milling process were investigated by using XRD,SEM and particle size analyzer,respectively.The results show that the peaks of powders gradually broadened and a solid solution formed after milling for 20 h.With the prolongation of the milling time,the grain size of milled powders decreased gradually,while both the micro-strain and the lattice parameters increased correspondingly.The powders were first rolled into flakes and agglomerated to form coarse composite powder particles by cold welding,and then,with the further prolongation of the milling time,these coarse particles gradually broke down into nearly spherical particles.After milling for 65 h,the particle morphology and microstructure of the alloy tended to be stable,and the particle size of nanocrystalline powders reduced to 5.80-776 μm,with the average grain size of the powders about 8 nm.