Nature of changes in the microstructure and properties of fine-grained iron-copper composites under heat treatment

We examine the nature of the changes that occur in the microstructure and p roperties of fine-grained iron-copper composites with 30 mass % (27.3 vol. %) Cu during solid-phase heat treatment and when passing through the meltin g paint of copper. Quantitative studies of the microstructure were made dur ing sintering of mixtures of the highly dispersed powders of the initial me tals and during heating of sintered high-density fine-grained specimens. Th e process of microstructure transformations during liquid-phase sintering a nd heating of high-density fine-grained composites above the melting point of copper was found to have three stages: recovery of the crystal structure and formation of large-angle boundaries in the Fe component, an increase i n Fe grain size, and formation of solid solutions by mutual diffusion of co mponents; penetration of the liquid phase along Fe grain boundaries with a decrease in grain size because of disintegration; and a secondary growth of Fe grains and formation of a Cu matrix structure or, more likely, a matrix structure of solid solution of Fe in Cu begins to form.