AUTOSTRESSES INDUCED BY POINT-DEFECTS IN SINTERING PHENOMENA - EFFECT ON MASS-TRANSPORT AND SINTERING STRESS

States of anelastic strain can be associated with excess concentrations of point defects, as generated by mass transport in a sintering compact. Correspondingly, states of mechanical long-range self-equilibrated stresses (''autostresses'') can be produced. The relationships between anelastic strain and autostresses have been derived for a two-particle model. A generalized relation between chemical potentials and autostresses, including surface stresses, is provided, which allows derivation of local thermodynamic driving forces for mass transport. The concept of equivalent external sintering stress, assumed to be the driving force for the global densification process, is shown to correspond, approximately, to the material- and history-dependent normal autostress component acting on the neck cross-sections. Predictions made from the model provide a new interpretation of experimental observations of the effect of gaseous phases, such as H2O and CO2, on the sintering of MgO and CaO powders.