Microstructural design and high temperature tensile deformation behaviour of 8mol% yttria stabilized cubic zirconia (8YCSZ) with SiO2 additions

Abstract In the present study, the microstructural evolution and high temperature deformation behaviours of 8 mol% Y 2 O 3 stabilized cubic zirconia (8YCSZ) containing up to 10 wt% SiO 2 is investigated. The experimental results show that the SiO 2 doped specimens sintered at 1400 °C contain only the cubic crystalline phase and SiO 2 has the very limited solubility of 0.3 wt% in cubic zirconia. This suggests that only small part of the SiO 2 dissolves in the cubic zirconia and the rest of SiO 2 segregates at grain boundaries and multiple junctions as amorphous (glassy) phase. This glassy phase prevents the grain growth by minimizing grain boundary energy and mobility, which results from solute segregation at the grain boundary and its drag. The deformation of the undoped 8YCSZ is characterized by large strain hardening with limited elongation. This is mainly due to severe grain growth during high temperature deformation. The addition of the SiO 2 results in a decrease in strain hardening and enhanced tensile elongation. These effects have been further improved with the increase of the SiO 2 addition reaching the elongation to failure of 152% for 10 wt% SiO 2 doped specimen in tension at a temperature of 1400 °C and strain rate of 1.3 × 10 −4 s −1 . The decreased strain hardening and increased ductility in the SiO 2 doped specimens are due to the segregation of amorphous glassy phase to the grain boundaries, thus hindering grain growth and facilitating grain boundary sliding, which is the primary mechanism of deformation in fine grained materials at high temperatures.