Mechanisms, Kinetics and Thermodynamics of Mechanical Alloying in Immiscible Fe-Mg System
E. P. YELSUKOV, G. A. DOROFEEV, A. L. ULYANOV and A. N. MARATKANOVA
Fysical-technical Institute, Ural Branch of the Russian Academy of Sciences,
Ul. Kirova 132, Izhevsk 426001 (Russia) E-mail: Yelsukov@fnms.fti.udm.ru
Pages: 191-196
Abstract
The processes involved in mechanical alloying (MA) of the mixture of Fe and Mg non-dissolving in equilibrium at the atomic ratio of 93 : 7 are studied by means of X-ray diffraction, Mössbauer spectroscopy, Auger electron and secondary ion mass spectrometry, chemical analysis of the composition. Surface enrichment of the powder particles with magnesium is observed at the first stage of MA. It is concluded that Mg gets segregated not only on the surface of particles but also within α-Fe grains. With a decrease in crystallite size (to ~10 nm), supersaturated solid solution of Mg in a-Fe is formed in the particles of the latter component, which is observed as an increase (to 0.288 nm) in the parameter of the bcc lattice and the appearance of additional components in the Mossbauer spectrum. It was established on the basis of model thermodynamic calculations that the driving force of the formation of solid solution in the system Fe-Mg may be the accumulated excess energy of coherent interphase boundaries of the Fe/Mg nanocomposite formed at the initial step of MA.
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