Study On Microwave Joining Of ZTM Ceramics/Fiber Braids And Its Elastic Behaviour

In order to meet the urgent requirements of high-temperature sealing materials inmodern industries and aerospace frontier field, an elastic sealing component withexcellent gas and thermal sealing functions at elevated temperatures was prepared bymicrowave joining the ZTM ceramics and alumina silica fiber braids, considering thegas sealing and bearing capacity of ZTM （zirconia toughened mullite） ceramics andcompressive and resilient properties of alumina silica fiber braids. Based on basicmaterials preparation and performance analysis, a high quality joining was realizedbetween ZTM and fiber braids in spite of their different temperature resistanceproperties. The compressive and resilient properties of joining components underdifferent loadings and temperatures were investigated, and the relative mechanismswere analyzed.The ZTM ceramics prepared by pressing process and conventional sinteringrevealed an excellent high-temperature strength which did not decrease withtemperature increasing. The fiber braids with three dimensions, four directions,45%volume fraction and45oweaving angle used in this experiment presented excellentcompressive and resilient properties. It was showed that the crystallizationtemperature of the fiber braids was about980oC and the crystallization, deformation,shrinkage or fusion would happen over1100oC. Therefore, the components could beused safely below1000oC.The process of microwave joining ZTM ceramics and fiber braids was studied.Through studying the temperature-rising characteristics, oxidization properties andphases analysis of micron level Al-Si alloy powders, an interface layer, includingpowders of Al-Si alloys、Al₂O₃、SiO₂and ZrO₂, was designed based on the microwaveselective heating characteristics. As a result, ZTM ceramics and fiber braids werejoined successfully with a microwave treating under2kW/60min.The results showed that the Al-Si alloy powders were heated rapidly, melt, oxidized,and finally formed mullite with other components due to their strong absorbingmicrowave ability. The interlayer and ZTM ceramics were joined effectively at hightemperature by heat-transmission, bonding and particles diffusion. However, fiberbraids had a relatively loose structure and weak microwave-absorbing ability. They were joined to the interlayer at low temperature about950oC owing to the chemicalreaction between molten Al-Si alloys and vitreous fiber at fiber braids interface.The compressive and resilient rules of component materials were studied underdifferent loads and temperatures. The results indicated that the materials were elasticunder0.1MPa between room temperature and600oC, and the resilient rates were100%. The resilience of materials at elevated temperature decreased with pressureincreasing. Under1MPa load, the materials were still full resilience below400oC,but the resilience-rate only retained30%at1000oC. The compressive and resilientmechanisms of joining materials were elastic resilience, anelasticity resilience andelastic-plastic resilience. The ultimate load at different temperatures, resiliencecharacteristics under different pressures, and elastic failure mechanism of materialswere analyzed, which provided a theory basis for the reliable application ofcomponent materials at elevated temperature.