MICROMECHANICAL STUDY ON THE MORPHOLOGY OF MARTENSITE IN CONSTRAINED ZIRCONIA

Either pure cooling induced martensitic transformation or pure stress assisted martensitic transformation in constrained zirconia in two mat erials with homogeneous (PSZ) and heterogeneous (ZTA) elastic and ther mal properties is investigated by the finite element method. The morph ology of the martensite (number of twin bands, relative thickness) det ermines the strain energy caused by the transformation which contribut es to the mechanical transformation barrier. In the case of small part icles the interface energy enters the transformation barrier, whereas for large particles it can be neglected. The thermodynamic existence c ondition predicts that the martensitic microstructure that is most lik ely to occur for the selected applied loading stress states is in good agreement with the experimental observations. (C) 1997 Acta Metallurg ica Inc.