STUDY OF NANOCRYSTALLINE AND AMORPHOUS POWDERS PREPARED BY MECHANICALALLOYING

The process of mechanical alloying consists of intimate mixing and mec hanical working of elemental powders in a high-energy ball mill. It ha s been well established that this process is able to produce nanocryst alline and amorphous material. In this study, the structural effects o f mechanical alloying of pure Fe, Fe50W50 and Fe50Mo50 powders were in vestigated by X-ray diffraction and Mossbauer spectroscopy. For all ca ses, nanocrystalline and/or amorphous fractions were found after milli ng. The resulting particle size was determined by X-ray diffraction. P ure Fe does not amorphize even after prolonged milling times. For the nanocrystalline powder, significant changes in the linewidth and the h yperfine field are found. Powder mixtures of Fe50Mo50 and Fe50W50 are completely amorphous after milling times of 10 h, as seen by Mossbauer spectroscopy, but nanocrystalline fractions of the non-iron part are still found in X-ray diffraction. Also in the amorphous state, further changes in the hyperfine parameters are found with increasing milling time.