Toughening mechanisms of ZTA ceramics at cryogenic temperature (77Â K)

ZTA ceramics containing 20 wt% ZrO2 were fabricated at different sintering temperatures (1450, 1500 and 1550 °C) by SPS and HP processes, respectively. The influence of sintering process on the mechanical properties of ZTA ceramics at 298 K and 77 K was investigated. It can be seen that the bending strength and fracture toughness of samples prepared by the two processes both improved at cryogenic temperature. The stress-induced martensitic transformation toughening mechanism was confirmed by the in-situ Raman technique. The tetragonal ZrO2 would be even more easy to transform because of the residual stress generated when temperature decreased from 298 K to 77 K. Therefore, the transformation toughening effect would become stronger, result in the increase of mechanical properties.