Grain Growth Kinetics And Mechanical Properties Of GPLs-ZrO₂-Al₂O₃ Composite Ceramics Prepared By Microwave Sintering

Al₂O₃-based composite ceramics have wide application in different industrial branches,however,high brittleness and low toughness have limited its use.The introduction of nanoscale particles into micron-sized matrix to fabricate micro-nano composite ceramics has become one of the ways to improve the mechanical properties of ceramics,and adding graphene simultaneously it is expected to obtain the high strength and high toughness Al₂O₃-based composite ceramics.In this experiment,Al₂O₃-based composite ceramics were prepared by doping with ZrO₂ and graphene,the relative densities,Vickers hardness,bengding strength,and fracture toughness of the sintered body were measured;the test instruments of metallographic microscope,scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer were used;and growth kinetics exponent and growth activation energy of Al₂O₃ columnar crystals are calculated using the phenomenological kinetic grain growth equation.The effect of ZrO₂ and GPLs in control principle,toughening mechanism and grain growth kinetics of microwave sintering process on Al₂O₃-based ceramics were discussed.The results show that during microwave sintering,nano-Zr O₂ can form a large number of“intracrystalline”structures in Al₂O₃ matrix,the mechanical properties of0.4GPLs-3ZrO₂-Al₂O₃ composite ceramics was good at 1500°C/30min,relative density was 98.76%,HV was 18.10GPa,K_ICC was 8.86MPa·m^1/2,and?_f was 517.11MPa.The fracture toughness is 138%higher than that of pure Al₂O₃ ceramic.By studying the effect of different additive on the growth kinetics of Al₂O₃ columnar grains,it can be seen that graphene inhibits the grain growth of Al₂O₃ significantly.When sintering at1500°C,the densification of 0.4GPLs-3ZrO₂-Al₂O₃ composite ceramics is mainly controlled by grain boundary diffusion,while pure Al₂O₃ ceramics and 3ZrO₂/Al₂O₃composite ceramics is dominated controlled by lattice diffusion in densification process.With the increase of graphene content in GPLs-3ZrO₂-Al₂O₃ series composite ceramics,the growth kinetics exponent of Al₂O₃ columnar crystal in major axis and in minort axis decreased,and the more the doping amount of graphene,the slower the growth rate in minor axis direction,which promote the growth of Al₂O₃ columnar crystals.The growth kinetic exponent of Al₂O₃ columnar crystals in major axis and in minort axis decreases with the increase of sintering temperature,and the growth activation energy increases with the increase of holding time in 0.4GPLs-3ZrO₂-Al₂O₃ composite ceramics,and the longer the holding time,the larger the growth trend of Al₂O₃ columnar crystals.Crack branching,crack deflection,crack bridging and pull-out of GPLs and“intracrystalline”ZrO₂ are the mian toughening mechanism.