Cold Sintering of Fe–Ag and Fe–Cu Nanocomposites by Consolidation in the High-Pressure Gradient

Abstract

The results of fabricating dense Fe–Ag and Fe–Cu nanocomposites from mixtures of powders consolidated by high-pressure cold sintering and from nanosized powders of silver (Ag), iron (Fe), and copper (Cu) are reported. The results of mechanical tests of Fe–Ag and Fe–Cu nanocomposites are presented. Nanocomposite powders were prepared by milling the micron powder of carbonyl iron (Fe) and nanosized silver oxide (Ag₂O) powder, as well as iron and cuprous oxide (Cu₂O) nanopowders in a high-energy attritor. The microstructure was investigated using a high-resolution scanning electron microscope. Compacts with a density of about 70% of the theoretical density were annealed in hydrogen to reduce silver oxide and cuprous oxide to metals and remove oxide films from the surface of iron powder particles. Then cold sintering followed—high-pressure consolidation at room temperature. The data on the pressure dependence of density of samples are found in a range of 0.25–3.0 GPa. Densities higher than 95% of the theoretical density are attained for all nanocomposites at a pressure of 3.0 GPa, while a density of about 100% is attained for Ag and Cu powders. High mechanical properties are found for all compositions in experiments for the three-point bending and for compression. It is established that mechanical properties of nanocomposites are noticeably higher than for composites formed from micron-sized powders. The higher plasticity was observed for Fe‒Ag and Fe–Cu nanocomposites when compared with the samples formed from nanostructured Fe.