Thermodynamics and microstructure of Ti–ZrO2 metal–ceramic functionally graded materials

The standard Gibbs free energy functions of Ti2O and Ti5O9 have been predicted according to the quasi-parabola rule. To determine the synthesis conditions of Ti–ZrO2 composite, the thermodynamic stability of various oxides in Ti–Zr–O system and the co-existing region of Ti and ZrO2 have been obtained by thermodynamic calculation. According to the thermodynamic analysis, it can be deduced that Ti could probably react with ZrO2 in the synthesis processes of Ti–ZrO2 functionally graded materials (FGMs). But the experimental results show that there is no reaction product in the Ti/ZrO2 interfaces and the bonding state between Ti and ZrO2 is physical in the composite. ZrO2 (3 mol.% Y2O3-stabilized zirconia) mainly exists as tetragonal phase in the prepared Ti–ZrO2 FGMs. The presence of Ti exerts an important influence on the transformation of ZrO2 from tetragonal to monoclinic phase. Ti–ZrO2 system functionally graded materials (FGMs) have been prepared by powder metallurgical method. The microstructural features of Ti–ZrO2 system FGMs have been appropriately interpreted by the heat percolation model.