APPLICATION OF STRENGTHENING TECHNICS FOR STEELS ON THE STRENGT OF CERAMICS

<ZrO_2>具有立方相、四方相和单相从高到低的多晶型<Y_2O_3>，当加入时，在室温下可得到四方相，并由于伴随体积膨胀的应力诱导四方相向单相转变的结果而显示出很高的韧性。这种陶瓷被称为部分稳定氧化锆，“PSZ”。类似的韧性机制可以在钢中找到。本研究将钢铁领域的增韧技术应用于陶瓷，特别是PSZ的增韧。首先用膨胀法和电子探针法测定了ZrO_2-Y_2O_3相图。并提出了新的图表。图中溶解度线的形状非常复杂。分析了其原因，认为四方相-立方相转变是一个准铁弹二级相变，四方相可以连续地转变为立方相，并随着相变的<Y_2O_3>缓和度的增加而增加。从相图上的这些新观点出发，阐明了淬火试样中的畴、马氏体组织、反相界和退火试样中的旋节分解等各种显微组织的形成机理，并在PSZ上进行了韧化试验。

<ZrO_2> HAS POLYMORPHS OF CUBIC,TETRAGONAL AND MONOCLINIC PHASES FROM HIGH TO LOW TEMPERATURES WHEN <Y_2O_3> IS ADDED, TETRAGONAL PHASE CAN BE OBTAINED AT ROOM TEMPERATURE,AND SHOWS VERY HIGH TOUGHNESS AS THE RESULTS OF STRESS INDUCED TRANSFORMATION FROM TETRAGONAL TO MONOCLINIC ACCOMPANYING WITH VOLUME EXPANSION. THIS CERAMICS IS CALLED PARTIALLY STABILIZED ZIRCONIA, "PSZ". SIMILAR TOUGHNING MECHANISM CAN BE FOUND IN STEELS. IN THIS STUDY, THE TOUGHENING TECHNIQUES DEVELOPED IN THE FIELD OF STEELS ARE APPLIED FOR THE TOUGHENING OF CERAMICS,ESPECIALLY PSZ. AT FIRST, ZIRCONIA-YTTRIA PHASE DIAGRAM WAS INVESTIGATED BY MEANS OF DILATOMETRY AND EPMA. AND NEW DIAGRAM WAS PROPOSED. THE SHAPE OF SOLUBILITY LINES IN THIS DIAGRAM IS VERY CHARACTERISTIC. THE REASON WAS CONSIDERED AND IT WAS CONCLUDED THAT THE TETRAGONAL-CUBIC TRANSFORMATION WAS A PARA-FERROELASTIC SECOND ORDER TRANSITION AND TETRAGONAL PHASE COULD BE TRANSFERED CONTINUOUSLY TO CUBIC PHASE WITH INCREASING EASING <Y_2O_3> CONTENTS. FROM THESE NEW ASPECTS ON THE PHASEDIAGRAM, THE FORMATION MECHANISMS OF VARIOUS MICROSTRUCTURES INCLUDING DOMAIN,MARTENSITIC STRUCTURES, ANTI-PHASE BOUNDATIES IN QUENCHED SPECIMENS AND SPINODAL DECOMPOSITION IN ANNEALED SPECIMENS WERE DISCUSSED,AND THEN THE TOUGHENING PROCESS WERE TRIED ON PSZ.