Possibility of Low-Temperature High-Strain-Rate Superplasticity in Fine-Grained Ceramic Materials

Abstract

For attaining high-strain-rate superplasticity (HSRS) in ceramic materials, prerequisites are described on the basis of existing knowledge about high-temperature plastic deformation and intergranular cavitation mechanisms. The knowledge suggests that a combination of grain-size refinement to 100-200 nm or smaller and enhanced diffusion caused by doping may highly enhance stress-relaxation around triple junctions and may lead to HSRS at temperatures lower than 1250-1300°C in structural ceramics. From this point of view, recent studies are reviewed and discussed on ceramic superplasticity at strain rates higher than 1 × 10⁻² s⁻¹. Attention is also placed on the fabrication of materials with nanosized grains and the resultant superplastic properties.