Phase Transformations in Dicalcium Silicate: I, Fabrication and Phase Stability of Fine‐Grained β Phase

Fine‐grained β‐Ca₂SiO₄ containing small amounts of sodium was fabricated as an analogue to tetragonal zirconia polycrystals (TZP) in order to study the stress‐induced β→γ transformation. This avoided the problems associated with the fabrication and evaluation of composites containing β‐Ca₂SiO₄. The microstructure of dense β‐Ca₂SiO₄ exhibited severe intergranular strains and twin‐terminating microcracks as seen by TEM. The β‐phase twin widths were quantitatively correlated with grain sizes giving an average ratio of 0.04. Stress‐induced transformation was observed on ground surfaces but not on fracture surfaces. The stress–strain behavior and the mechanical properties were consistent with stress‐induced microcracking and microcrack coalescence. The elastic modulus of fully dense β phase was estimated to be 123 GPa.