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Published March 15, 1993 | public
Journal Article Open

Mechanically driven alloying and grain size changes in nanocrystalline Fe-Cu powders


Highly supersaturated nanocrystalline FexCu100-x alloys (10 less-than-or-equal-to x less-than-or-equal-to 95) have been prepared by mechanical alloying of elemental crystalline powders. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The results are compared with data for ball-milled elemental Fe and Cu powders, samples prepared by inert gas condensation, and sputtered films. The deformation during milling reduces the grain size of the alloys to 6-20 nm. The final grain size of the powders depends on the composition of the material. Single-phase fcc alloys with x less-than-or-equal-to 60 and single-phase bcc alloys with x greater-than-or-equal-to 80 are formed even though the Fe-Cu system exhibits vanishingly small solid solubilities under equilibrium conditions. For 60 less-than-or-equal-to x less-than-or-equal-to 80, fcc and bcc solid solutions coexist. The alloy formation is discussed with respect to the thermodynamic conditions of the material. The role of the large volume fraction of grain boundaries between the nanometer-sized crystals, as well as the influence of internal strains and stored enthalpies introduced by ball milling, is critically assessed.

Additional Information

Copyright © 1993 American Institute of Physics. Received 24 March 1992; accepted 21 September 1992. This work was supported by the U.S. Department of Energy (DOE Contract No. DEFGO386ER45242). Special thanks are given to P. Carpenter and C. Garland for technical assistance, and to Y. R. Abe, R. Birringer, and B. Fultz for stimulating discussions and effective cooperation.


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