Characterization of copper–cementite nanocomposite produced by mechanical alloying

A copper–iron carbide nanocomposite has been synthesized by high-energy milling of elemental powders (Cu69–Fe23–C8), followed by annealing at 873 K. Phase identification and microstructure characterization have been carried out by transmission electron microscopy and energy dispersive spectroscopy. The carbide phase found in the as-milled material has been identified as Fe3C and/or Fe7C3, but clearly only Fe3C was present after annealing. Overall, grain sizes ranged from 10 to 50 nm in the as-milled condition and from 30 to 160 nm after annealing, with the carbide phase presenting a higher growth rate than copper. Stacking faults and a dispersion of Cu nanoparticles (5–10 nm) have been detected in annealed cementite while copper grains exhibited twins on 1 1 1 planes. Cementite growth could be evaluated in terms of precipitate growth theory. The remarkable thermal stability of the copper matrix is proposed to be related to solute drag effects.