Механика машин, механизмов и материалов (Mar 2020)
Preparation of Composite Nanostructured Powders Based on Copper and Iron by Mechanochemical Synthesis
Abstract
It is shown that the formation of a solid solution is observed passing through the stage of formation of the nanocomposite during the mechanochemical synthesis of copper- and iron-based composites with a low-melting component (bismuth, gallium, tin, indium). At the same time, it passes through the formation of intermediate intermetallic compounds in inter-acting metal systems. It is shown that there are significant differences in the kinetics of formation of products of mechanosynthesis for powder mixtures based on iron and copper that can be explained by the difference of evolution of dislocation structure in body-centered cubic (BCC) (iron) and face-centered cubic (FCC) (copper) crystal lattices under plastic deformation shear under high pressure during the early stages of mechanical activation, as well as by the difference of the structure of the forming nonequilibrium boundaries that affects their diffusion permeability and grain boundary self-diffusion coefficient. At the same time, FCC structures are characterized by higher values of these parameters, which in this case contributes to a faster formation of mechanosynthesis products. It was found that the mechanical activation of iron and copper powders with refractory metals (Me – Ti and Zr) allows to produce mechanocomposites Cu/Me and Fe/Me with a homogeneous distribution of the nanosized components (zirconium and titanium) along the boundaries of iron and copper grains without significant interaction between them. Under conditions of intensive mechanical processing, redox reactions occur in copper (iron) – active metal (Zr, Ti) systems with the formation of dispersed oxides of active metals in a matrix of copper and iron. The use of mechanocomposites with zirconium in reactions with copper and iron oxides leads to the formation of copper, iron metals and zirconium oxides, and the use of mechanocomposites with titanium contributes to the formation of complex oxides. Such difference in the kinetics of phase formation during mechanical activation is due to the different solubility of zirconium and titanium in iron and copper matrices.
