Liquidlike sintering behavior of nanometric Fe and Cu powders: Experimental approach

Nanometric Fe and Cu powders were sintered in vacuum, He, and H-2 atmospher es after uniaxial cold pressing. The shrinkage behavior of samples was stud ied using three different dilatometric techniques: constant heating rate, i sothermal annealing, and the Dorn method. Density greater than 90 pet was o btained at sintering temperatures of 900 degrees C. In nanometric powders, densification and grain coarsening occurred in a narrow temperature interva l. Despite the low oxide content in the starting powders (1.5 to 4 wt pet), the reducing atmosphere plays a relevant role in the sintering process. Th e self-diffusion activation energies obtained for nanometric Fe were 116 an d 60 kJ/mole in vacuum and H-2, and those obtained for nanometric Cu were 7 0 and 43 kJ/mole in He and H-2. According to the present results, the activ ation energies obtained from both nanometric powders in H-2 could be associ ated with those for self-diffusion in liquid Fe (65 kJ/mole) and Cu (41 kJ/ mole).