Microstructural evolution during liquid phase sintering: Part I. Development of microstructure

During liquid phase sintering, numerous solid-solid particle contacts can be generated by particle motion within the fluid. It is shown that, somewhat surprisingly, Brownian motion can produce such contacts. If such contacts are accompanied by particle adherence, the particles can then subsequently fuse into one (i.e., coalesce) by the liquid state analog of the evaporation-condensation mechanism of sintering. An isolated microstructure will develop if the time for particle coalescence is much less than the time between contacts. A highly skeletal arrangement of particles will form under the converse condition. Using these principles, a “microstructure map” is calculated in which the expected morphology of microstructure (i.e., skeletal or isolated) is related to the solid particle volume fraction, the kinetic and thermodynamic parameters affecting particle coalescence, and the frequency of particle contacts by Brownian motion. Some discussion of the thermodynamic and morphological factors affecting the probability of particle adherence after contact is presented.