Mechanism of the sintering of high-porosity materials in the presence of a volatile pore-forming agent

Abstract

1. During the sintering of compacts with a filler, their volume shrinkage is a result of the densification of the regions with the fine natural pores, but their macroporosity remains unchanged (except in the case of compacts of very high starting porosity). 2. A matrix mixture of metal and voids predominates in the structure of porous solids produced with a coarse filler, while a statistical mixture is characteristic of the structure of solids produced with a fine filler. A formula is proposed for calculating the statistical weight of the matrix mixture in the structure. 3. The differences in the structures of porous materials associated with the particle size of the filler lead to differences in the structural weakening of these materials (the volume viscosity is less for porous solids with a mainly statistical distribution of the large pores), and this results in a decrease in macroporosity during the sintering of compacts with a fine filler. 4. The growth of interparticle contacts during the sintering of compacts with a filler is analogous to the growth of contacts in unpressed powders being sintered and is directly determined by the kinetics of the volume shrinkage of the porous solids.