Determination of the mechanical response of sintering compacts by cyclic loading dilatometry

Determination of the mechanical response of a powder compact during densification is critical in analyzing defect formation and macroscopic dimensional changes, particularly in systems where constrained sintering is involved. Cyclic loading dilatometry is proposed as a novel approach in evaluating the mechanical response of the sintering compact, including sintering pressure, elastic modulus, and viscosity. The advantage of this technique is that only one experiment is needed to determine the equilibrium elastic and viscous properties of a sintering material at any temperatures for any given heating schedule, and no interrupted tests are necessary. This methodology is demonstrated for sintering compacts of Al₂O₃, Ce-TZP, and their composite mixture. The loading dilatometric data showed that the compact behaved elastically prior to the onset of sintering and during the very initial stages of sintering, which was followed by a transition leading to a viscous behavior for the latter part of the densification. Application of different load levels, ranging from 0.25 to 1 MPa, showed that the compact viscosity is essentially linear within the applied stress range at temperatures greater than 1100°C.