

Author: Dominguez O. Champion Y. Bigot J.
Publisher: Springer Publishing Company
ISSN: 1543-1940
Source: Metallurgical and Materials Transactions A, Vol.29, Iss.12, 1998-12, pp. : 2941-2949
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Abstract
Nanometric Fe and Cu powders were sintered in vacuum, He, and H2 atmospheres after uniaxial cold pressing. The shrinkage behavior of samples was studied using three different dilatometric techniques: constant heating rate, isothermal annealing, and the Dorn method. Density greater than 90 pct was obtained at sintering temperatures of 900 °C. In nanometric powders, densification and grain coarsening occurred in a narrow temperature interval. Despite the low oxide content in the starting powders (1.5 to 4 wt pct), the reducing atmosphere plays a relevant role in the sintering process. The self-diffusion activation energies obtained for nanometric Fe were 116 and 60 kJ/mole in vacuum and H2, and those obtained for nanometric Cu were 70 and 43 kJ/mole in He and H2. According to the present results, the activation energies obtained from both nanometric powders in H2 could be associated with those for self-diffusion in liquid Fe (65 kJ/mole) and Cu (41 kJ/mole).
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