| Eutectic oxide ceramics possess excellent mechanical properties,which have attracted the attention of many researchers in recent years,but it is difficult to make large and complex eutectic components by direct solidification technology.The eutectic powders,which are produced by directional solidification technology,have been consolidated by conventional sintering,hot press sintering,spark plasma sintering and other technologies,however,it requires high temperature or high temperature/high pressure conditions to produce eutectic ceramics parts.Therefore,it is necessary to prepare excellent ceramic composites with eutectic composition by using a novel flash sintering technology which has the advantage of low sintering temperature and short sintering time.In this paper,Al2O3/YAG ceramic composites have been investigated carefully.The X-ray diffractometer is used to investigate the phases of the sample during sintering.The morphology and mechanical properties of the flash sintering samples were tested by using scanning electron microscopy and Vickers hardness tester.The main research work is as follows:?1?By comparing the phases of the samples treated with different furnace temperature and holding time on the Al2O3/Y2O3 green body by conventional sintering,it indicated that both the furnace temperature and holding time will affect the reaction progress of Al2O3 and Y2O3.The results show that the reaction progress of Al2O3 and Y2O3 is related to furnace temperature.The higher the furnace temperature,the reaction between Al2O3 and Y2O3 is more deeper.The reaction progress of Al2O3 and Y2O3 is also related to the holding time.Under the same furnace temperature,the longer holding time,the extent of phase transformation is more higher.?2?The effect of electric field strength on phase transformation is investigated by comparing the change of the phases of the samples,which is prepared by conventional sintering,field-assisted sintering and flash-sintering at the same sample temperature.The results show that the electric field strength can accelerate the rate of phase transformation in Al2O3/YAG composite ceramics.Compared with conventional sintering,the phases transformation is more complete with a large electric field strength applied on the sample,even no current is required in the sample.Compared with the conventional sintering,the phases tranformation of the flash sintered sample is more complete under the same heating and cooling rate,holding time,and sample temperature.?3?By comparing the oneset of flash sintering conditions of the Al2O3/Y2O3 green body and the Al2O3/YAG green body,it indicated that the solid-state reaction will affect the oneset of flash sintering conditions.The results show that compared with the flash sintering of Al2O3/Y2O3,the flash sintering of Al2O3/YAG requires higher furnace temperature and higher electric field strength,hence,the solid-state reactions can reduce the conditions to active the oneset of flash sintering.?4?By flash sintering Al2O3/Y2O3 samples with different molar ratios using different holding time,it indicates that the oneset of flash sintering is related to the intermediate phases of YAM and YAP.The results show that the change of YAG content of the sample has no obvious effect on the oneset of flash sintering.The lower oneset conditions of flash sintering of the Al2O3/Y2O3 composite ceramics is caused by the intermediate phases YAM and YAP.?5?The advantages of the flash sintering process are explored by comparing the dense samples,which are prepared by the flash sintering,conventional sintering at the same sample temperature,and directional solidification technique.The results show that the flash sintering process requires shorter time and lower furnace temperature than conventional sintering to prepare a dense Al2O3/YAG ceramic composites.Compared with the Al2O3/YAG eutectic ceramics prepared by the directional solidification technique,the flash sintered Al2O3/YAG ceramic composites have a lower hardness.However,the fracture toughness is better than the eutectic ceramic.This shows that the flash technology can be used to prepare high quality Al2O3/YAG ceramic composites. |
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