Ceramics Superplasticity and High-Temperature Deformation Theory of Sintering

Superplasticity is the ability of polycrystalline solids to exhibit exceptionally large tensile elongation at high temperatures, governed primarily by grain-boundary sliding and relative motion of fine grains. While widely exploited in metals for near-net-shape forming, ceramics have long been regarded as intrinsically brittle. This view was overturned by the first discovery of superplasticity in zirconia in 1985, followed by demonstrations in many fine-grained ceramics, including zirconia/alumina composites, silicon nitride, etc. Despite early expectations for improved ductility and forming rate, industrial adoption has remained limited because most ceramic components can be manufactured efficiently by conventional powder forming and sintering. In parallel, sintering theory has advanced by reinterpreting densification as high-temperature deformation driven by sintering stress, linking creep/superplasticity concepts with continuum mechanics. Recent progress in 3D synchrotron X-ray tomography, large-scale simulations, and emerging sintering technologies motivates a multiscale reconstruction of sintering theory. This article highlights selected topics closely related to the author’s research and a new graduate-level textbook on sintering fundamentals.