Microstructure and indentation properties of ZrO2/Ti functionally graded materials fabricated by spark plasma sintering

This study aims to investigate effects of compositional gradation patterns and amount of Y2O3 stabilizing ZrO2 on microstructure and nano- and micro-indentation properties in ZrO2/Ti functionally graded materials (FGMs) fabricated by spark plasma sintering (SPS) methods. 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 in the FGMs are high compared to those in Ti substrates, which can be attributed to the presence of titanium oxides in Ti phase. 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 the fabrication. Indentation properties and thermal stress states have been examined based on a mean-field micromechanics-based model.