Combined effects of interstitial and Laplace pressure in hot isostatic pressing of cylindrical specimens

Laura Galuppi & Luca Deseri, JoMMS, Vol. 9, No. 1, 2014
dx.doi.org/10.2140/jomms.2014.9.51

http://www.ing.unitn.it/~deseril/

Sintering of precompacted metallic and ceramic micro and nanopowders is a complex problem influenced
by several factors. We quantify the influence of both local capillary stresses acting at the surface
of one pore or particle (usually referred to as Laplace pressure) and the gas pressure in pores during
sintering of precompacted metallic (micro/nano)powdered cylinders. The latter influences only the third
phase of sintering, that is, the phase in which the porosity is closed.
The isostatic pressing loading mode, which also covers the case of free sintering, is considered.
Whereas the Laplace pressure is demonstrated to have a beneficial effect on sintering, the gas pressure
acts against the reduction of the porosity, causing an increase in sintering time. This contribution could
reach the sum of the stress due to loading and the interstitial pressure, thereby preventing the desired
porosity to be reached.
For the sake of illustration, a specific aluminum-zinc-magnesium-copper alloy is examined in this
paper. The purpose is to estimate the effects of sintering time and residual porosity and to determine
thresholds under which the contributions described above are negligible. In order to determine the effects
of Laplace and gas pressure in pores on the stability of the process, a high-order perturbation analysis
has been performed.