Weibull Distribution Of The Fracture Strength Of99%Alumina Ceramic Reshaped By CIP

The mechanical reliabilities of99%alumina ceramics preformed by dry pressing usingvarious pressures and reshaped by cold isostatic pressing (CIP) at150MPa are investigated.After being dried, green bodies are sintered at1500℃,1520℃,1540℃,1560℃and1580℃respectively at atmospheric pressure. After sintering, analyze the XRD, the SEM of thesamples, at the same time, test each sample of fracture strength, shrinkage and bulk density.Using both linear regression and the maximum likelihood method the value of theweibull modulus, evaluate the reliability of99alumina ceramics.Results show that when the dry pressing preforming pressure of75MPa, isostatic pressingmolding pressure of150MPa, the sintering temperature is1580℃,99alumina ceramics hasgood internal microstructure, flexural strength of minimum discreteness, weibull modulusmaximum, the most stable performance, under the preparation technology and fracture strengthvalue is not more than an average of260MPa. When using the method of linear regressionestimation, weibull modulus in dry pressing preforming pressure of75MPa, isostatic pressingmolding pressure of150MPa, when the sintering temperature of1580℃, weibull modulusvalue is maximum to15.79. When using maximum likelihood estimation method to estimatethe weibull modulus is also under the same processing parameters and the sintering temperaturereached the maximum value13.9974. Maximum likelihood method not only can evaluateceramics discreteness of flexural strength, can also evaluate the stability of the ceramic materialperformance.According to the best molding process, a preliminary study of99%alumina ceramicsfiring curve, make preparation of alumina ceramics to meet reliability on the basis of improvingits fracture strength. Firing curves to set up four factors three levels orthogonal experiment,obtained by the orthogonal experiment the best firing curve of99%alumina ceramics. At thesame time, to improve the best curve, burn a certain number of ceramic samples. Test eachsample of flexural strength, shrinkage and bulk density, fracture strength value of the highest99alumina sintering curve.The results show that the99%alumina ceramic sintering curve: RT~300℃,1.5℃/min.300℃~750℃,2℃/min.750℃~1000℃,2℃/min.1000℃~1400℃,10℃ /min.1400℃: thermal insulation for30min;1400℃~1500℃,10℃/min.1500℃~1580℃,2℃/min. Fired under1580℃: thermal insulation for60min in the sample withgood microstructure and grain growth is evener, grain boundary clear, internal porosity isrelatively small flexural strength of273.28MPa.