Phase Transformation and Grain Refinement of Yttria Stabilized Zirconia During Multi-Cyclic Nanoindentation

Abstract

The microstructural changes of yttria stabilized zirconia (YSZ) under repetitive loading/unloading were investigated by multi-cyclic nanoindentation. Raman spectroscopy analysis revealed that a tetragonal-to-monoclinic (t-m) phase transformation occurred, and multi-cyclic indentations promoted this transformation more significantly than single indentations. Scanning transmission electron microscopy revealed that phase transformation occurred beneath the free surface outside the indents, whereas grain refinement was dominant beneath the indenter tip. In addition, deformation analysis demonstrated that the t-m phase transformation occurred during unloading rather than loading. Based on the experimental results, a distribution model of phase transformation and grain refinement was established.