Nano- and Micro-Indentation Characterization of ZrO2 / Ti Functionally Graded Materials Fabricated by Spark Plasma

Abstract — This study aims to investigate nano- and micro-indentation properties of ZrO2/Ti functionally graded materials (FGMs) fabricated by spark plasma sintering (SPS). The experimental results demonstrate that the amount of Y2O3 in ZrO2 largely affects the microstructure and hardness in the FGMs. FGMs with ZrO2 containing noY2O3 has not been soundly fabricated because of transformation of ZrO2 during the cooling processes. In terms of effect of compositional gradation patterns, higher ZrO2 content corresponds to higher micro-Vickers hardness, while nanoindentation elastic modulus and hardness in both ZrO2 and Ti phases are independent of constituent phase content in the FGMs. Nanoindentation elastic modulus and hardness in Ti phase are as high as those in ZrO2 phase, which may be attributed to presence of titanium oxides in Ti phase in FGMs. Such indentation properties have been examined based on a mean-field micromechanics-based model