Finite element analysis on flexural strength of Al2O3-ZrO2 composite ceramics with different proportions

Al2O3-ZrO2 composite ceramics with different proportions were fabricated by isostatic compaction and sintered by the normal pressure sintering method. The effect of proportions on the microstructures, mechanical properties and sintering properties of Al2O3-ZrO2 ceramics were investigated. The results show that as the volume fraction of ZrO2 increases from 0% to 50%, the relative bulk density gradually decreases from 90% to 88.5% and the porosity increases from 0.182% to 0.197%, but the flexural strength increases from 291 to 423 MPa. In order to explain this “abnormal phenomenon”, a finite element method was applied to calculate the maximum tensile stress on the Al2O3-ZrO2 grain interface under tensile condition for the first time. The results indicate that the maximum grain interface tensile stress (MTS) of the Al2O3-ZrO2 composite gradually decreases from 148.18 to 96.89 MPa as the volume fraction of ZrO2 increases from 25% to 100%, which may be the main reason for their progressive flexural strength of Al2O3-ZrO2 composite from 320 to 604 MPa. In addition, the pure Al2O3 model has low MTS, and its ceramic material also has good sintering performance, but its flexural strength is worst compared to other Al2O3-ZrO2 composite ceramics. This is due to the large sizes of defects generated by abnormal growth of Al2O3 particles.