Isothermal martensitic transformation of zirconia doped with small amount of yttria

Abstract
The high temperature tetragonal phase of zirconia containing 1.45-1.60mol% of yttria can be fully retained at room temperature by rapid cooling. The metastable phase transforms into the stable monoclinic phase either isothermally or athermally depending on being heated or subzero cooled. The behavior of the isothermal transformation was studied. Dilatometric measurement resulted in a typical sigmoidal curve after some incubation time. The transfonnation start time exhibited a C curve in TTT diagram. The C curve shifted toward the short time side as weil as toward the high temperature side with decreasing yttria content or increasing grain size. An interruption/resumption experiment of the isothermal heating revealed that the total time expended before the initiation of the transformation was nearly constant regardless of the interruption.