Thermal-electrical-structural Coupled Analysis For Superplastic Forming And Spark Plasma Sintering Of Sialon/Si₂N₂O Nanocomposite

Spark plasma sintering is a new technology of preparation new functional materials,which has fast heating, short sintering time, controllable organization, energy saving andenvironmental protection and other features. As spark plasma sintering process andequipment development, the study on SPS mechanism has becom one of the importantfoundation throry in the powder metallurgy field. The Sialon/Si₂N₂O ceramics is preparedby the technology of SPS and use discharge superplastic forging forming process to makeSialon/Si₂N₂O gear in this paper. After the test, we got temperature, current, voltage,displacement curve. The spark plasma sintering of the two tests are simulated by Marcsoftware on the basis of the experiment results, and got the temperature, relative densityand stress distribution rules of the sample.Using spark plasma sintering process, we can get Sialon/Si₂N₂O ceramics under theconditions of1150℃preservation7min,1240℃preservation7min, and1300℃preservation2min. Then the spark plasma sintering of the material of Sialon/Si₂N₂Oceramic is simulated by Marc software on the basis of the experiment results and that theequivalent radiation coefficient was determined, and we got the temperature, relativedensity and equivalent stress distribution rules of the sample in initial heat preservationstage and final heat preservation stage. In initial heat preservation stage, sinteringtemperature reached the required value, the temperature difference is larger and therelative density of powder is lower. But in initial heat preservation stage, the temperatureof powder distributed more evenly, the value difference is smaller and the relative densityis higher because of after a period of heating preservation; the temperature is the highestand more densification in the center of the sample; the faster SPS sintering temperature,the sintering current is higher, and the distribution of temperature, relative density, stressof the powder is more nonuniform; the equivalent stress is small during the Sialon/Si₂N₂Onano-ceramic forging forming, less than10MPa.We got Sialon/Si₂N₂O ceramic gear with SPS forging forming process under theconditions of1200℃and the process is simulated on the basis of the test results.Becauseof the gear ultra low temperature superplasticity, so the deformation liquidity is good, the front tooth embossment is not serious and the whole addendum flow velocity difference issmaller; the gear temperature distribution is same as the cylindrical sample sintered; gearcenter part of the relative density is bigger, but gear surface relative density minimum;thelarger stress occurring in the dedendum circle and the tooth intersection position, where isthe initial position of the materials flows into the tooth cavity during deformation process,the upper and lower suaface as well as the tooth flank and the die cavity contact regions ofthe equivalent stress is also larger.