On the Limit of Metals Disintegration by Method of Mechanical Dispersion
LEONID V. VASILIEV1 AND SVETLANA F. LOMAYEVA2
1Udmurtia State University, Ul. Universitetskaya 1, Izhevsk 426032 (Russia), E-mail: lvas@uni.udm.ru
2Physical-Technical Institute, Ural Centre of the Russian Academy of Sciences,
Ul. Kirova 132, Izhevsk 426001 (Russia)
Pages: 203-212
Abstract
Mechanisms restricting the possibility to increase dispersity of powders produced by mechanical grinding method have been considered. Transformation of nanocrystal powder particles into super-plastic state has been demonstrated to be the main mechanism, whereupon disintegration stops, and all further treatment amounts to change in the shape of particles. Through introduction the notion of macro-dislocation - the linear defect of irregularity in the nanocrystal grain packing - both the process of transformation into super-plastic state and the process of disruption are described. Estimations of disintegration limit for metal powders have been made. Results are in good agreement with experimental data obtained by atomic power microscopy method (APM) on the iron powder ground with surface-active substances (SAS) added. A sketch of formation and development of nanostructure and phase constitution of powder particles being ground in ball mills in liquid organic media has been suggested, which takes account of the process features connected with multiple high-velocity cold-hardening, high temperature polygonization and re-crystallization, and multiple re-chill in liquid media.
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