The Effect Of Sintering AIDS On Mechanical Properties Of 3Y-TZP/Al₂O₃ Composite Ceramics

Due to ZrO₂ ceramics have the advantages of high strength,high hardness,corrosion resistance,low thermal conductivity,and low coefficient of thermal expansion,they are widely used in functional ceramics and structural ceramics.Among them,3 mol.%Yttria-stabilized zirconia（3Y-TZP）has attracted the attention of scholars for relatively excellent mechanical properties,but low-temperature anti-aging performance is general,which limits further development and application.Therefore,the researchers adopted the method of adding Al₂O₃ with high elastic modulus and high hardness to the 3Y-TZP ceramic to improve mechanical properties.However,both Al₂O₃ and ZrO₂ are high-melting oxides with melting points above 2000°C.It is difficult to prepare 3Y-TZP/Al₂O₃ composite ceramics with high density and good mechanical properties under normal pressure sintering.The sintering aids can not only reduce the sintering temperature of complex ceramics,but also can improve the mechanical properties.In this study,high-energy ball milling method was used to prepare 3Y-TZP nano-powder,which was mixed with nano-Al₂O₃ powder for ball milling,and sintering aids MnO₂-CeO₂ and TiO₂-MgO were added,respectively.Under normal pressure,the final ceramic samples were obtained after sintering at 1550°C for 3h.The X-ray diffraction（XRD）and field emission scanning electron microscope（FESEM）were used to analyze the phase composition and micromorphology.Using vickers micro-hardness tester,electronic universal testing machine and other testing instruments to characterize the vickers hardness,fracture toughness and three-point bending strength of the composite ceramics.The influence of sintering aids on the mechanical properties of multiphase ceramics was analyzed,and the related mechanism was discussed.The results show that adding sintering aids to the 3Y-TZP/Al₂O₃ multiphase ceramics helps to reduce the pores existing between the second phase Al₂O₃ grains and the main phase ZrO₂ grains,making the multiphase ceramics sintering denser and mechanical properties will also be improved.Adding MnO₂ and CeO₂ to the 3Y-TZP/Al₂O₃ composite powder can improve the mechanical properties of the composite ceramics.With the increase in the amount of MnO₂added,a small amount of monoclinic phase appears in ZrO₂,the hardness of the complex-phase ceramics shows a downward trend,and the maximum vickers hardness is 17.6 GPa.When the amount of MnO₂ added is 0.4 wt.%and CeO₂ is 0.6 wt.%,the toughness reaches the maximum value of 8.3 MPa·m^1/2.The bending strength curve of the material rises and then falls,the maximum value is 818.4 MPa.After adding the composite sintering aids TiO₂ and MgO to the 3Y-TZP/Al₂O₃ powder,it also contributes to the density of the material and its mechanical properties will be improved.According to the experimental results,as the content of TiO₂ increases and the content of MgO decreases,the content of m-ZrO₂ in the composite ceramics gradually increases,which is detrimental to mechanical properties.The measured maximum hardness value is 17.6 GPa.The fracture toughness of the composite ceramics reaches 7.8 MPa·m^1/2after adding 0.3 wt.%TiO₂ and 0.7 wt.%MgO.The maximum measured three-point bending strength is 740.9 MPa.In summary,the addition of sintering aids in 3Y-TZP/Al₂O₃ not only helps the sintering to be dense,but also improves mechanical properties.The addition of sintering aids MnO₂-CeO₂ have a better effect on the fracture toughness and bending strength of composite ceramics than that of TiO₂-MgO,which also provides a certain direction for the development of Al₂O₃reinforced ZrO₂ ceramics.