Cold sintering of Fe-Ag and Fe-Cu by consolidation in high pressure gradient

The paper states the results of obtaining Fe—Ag and Fe—Cu dense nanocomposites from composite powders consolidated by cold sintering in the high pressure gradient, as well as from nanosize powders of silver (Ag), iron (Fe) and copper (Cu). The results of mechanical tests conducted on Fe—Ag and Fe—Cu nanocomposites are provided. Nanocomposite powders were obtained by high energy attrition milling of carbonyl iron (Fe) micron scale powder and nanosize silver oxide powder (Ag2O), as well as iron and cuprous oxide (Cu2O) nanopowders. High resolution scanning electron microscopy was used to study the microstructure. Compacts featuring approximately 70 % of full density were annealed in hydrogen atmosphere to reduce silver and cuprous oxides to metals and to remove oxide layers from the surface of iron powder particles. This was followed by cold sintering — consolidation under high pressure at a room temperature. The data on specimen density dependence on pressure in the range of 0,25 —3,0 GPa were obtained. Densities were above 95 % of the full density for all nanocomposites, and close to 100 % of the full density under 3,0 GPa for Ag and Cu powders. High mechanical properties in three-point bending and compression were observed for all nanocomposites. It was found that mechanical properties of nanocomposites are substantially higher as compared with composites obtained from micron scale powders. Higher ductility was observed in Fe—Ag and Fe—Cu nanocomposites as compared with specimens obtained from nanostructured Fe.