A theoretical study of grain growth in porous solids during sintering
- Fraunhofer-Inst. fuer Werstoffmechanik, Freiburg (Germany)
The processes of grain boundary migration, pore drag and pore/boundary separation are described on the basis of the phenomenological equations for boundary migration and surface diffusion. Cylindrical pores on triple grain junctions are assumed to represent the open porosity during intermediate-stage sintering. It is found that cylindrical pores can hardly detach from migrating boundaries. Three-dimensional closed pores, however, which predominate during final stage sintering, can separate from migrating grain junctions. The separation process is modeled numerically and the conditions for separation are formulated. Analytical approximations for the pore mobility are shown to describe the numerical results well. They serve to establish effective mobilities of grain boundaries bearing pores in various configurations. Classical theories of grain coarsening are modified by using these effective mobilities. Mechanical constitutive models of sintering contain the grain size as an internal variable. The present analysis leads to an evolution equation for the average grain size, which depends on the volume fraction of the pores and on their configuration.
- OSTI ID:
- 6466645
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 41:6; ISSN 0956-7151; ISSN AMATEB
- Country of Publication:
- United States
- Language:
- English
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ANALYTICAL SOLUTION
DATA
DIFFUSION
FABRICATION
GRAIN BOUNDARIES
GRAIN GROWTH
GRAIN SIZE
INFORMATION
MATERIALS
MATHEMATICAL MODELS
MICROSTRUCTURE
NUMERICAL DATA
NUMERICAL SOLUTION
POROSITY
POROUS MATERIALS
SINTERING
SIZE
THEORETICAL DATA