The structure of nanocrystalline Fe, W and NiAl powders prepared by high-energy ball-milling

Fourier analysis of the profiles of the peaks in the powder patterns of Fe, W and NiAl yielded particle sizes as low as 35 Angstrom and strains as high as 1.10% after mechanical working in a high-energy ball-mill. The atomic distribution functions G(r), determined from the entire diffraction patterns, showed no significant peaks beyond 35 to 50 Angstrom. Micron size powders of Fe, W and NiAl were mechanically worked in a high-energy ball-mill for milling times up to 100 h. The diffraction patterns were recorded with Co and Mo Ka: radiation and a Ge solid state detector. Using the Warren-Averbach method, the sizes <D> and Dr of the coherently diffracting domains (x-ray particle size) were determined from the slopes and sums of the particle size Fourier coefficients, respectively, and the root-mean-square strains <(epsilon(L))(2)>(1/2) were calculated from strain coefficients as a function oft. The diffraction patterns in the range of Q = pi(sin theta)/lambda = 1 to 15 Angstrom(-l) were used to evaluate the total structure factors I(Q) and the reduced atomic distribution functions G(r).