Vol. 9, No. 1, 2014

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ISSN: 1559-3959
Combined effects of interstitial and Laplace pressure in hot isostatic pressing of cylindrical specimens

Laura Galuppi and Luca Deseri

Vol. 9 (2014), No. 1, 51–86
Abstract

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.

Keywords
sintering, powder technology, nanopowders, hot isostatic pressing, interstitial and Laplace pressure, ceramic compaction, metallic powder compaction
Milestones
Received: 8 July 2013
Revised: 9 September 2013
Accepted: 6 October 2013
Published: 23 March 2014
Authors
Laura Galuppi
Dipartimento di Ingegneria Industriale
Università degli Studi di Parma
Viale G. P. Usberti 181/A
43124 Parma
Italy
Luca Deseri
DICAM, Group of Solid and Structural Mechanics
University of Trento
via Mesiano 77
38123 Trento
Italy
Department of Civil and Environmental Engineering and Department of Mechanical Engineering
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213
United States
Department of Nanomedicine
TMHRI-, The Methodist Hospital Research Institute
6565 Fannin Street
MS B-490
Houston, TX 77030
United States