Investigation On The Fabrication, Microstructure And Properties Of Al₂O₃/Ti₃SiC₂Composites

In this paper，Ti，Si and carbon black were used as raw materials，with Al₂O₃asadditive，to fabricate Al₂O₃/Ti₃SiC₂composites by the method of hot-pressing. XRD,SEM and EDS were used to study the phase constituent, microstructure, mechanicalproperty and oxidation resistance of Ti₃SiC₂and Al₂O₃/Ti₃SiC₂composites. The resultswere described as follows:（1） The results of XRD showed that: The main phase of synthesized Ti₃SiC₂sample is Ti₃SiC₂，along with a small amount of impurity phase TiC，and the oxidationproduct of sample T is TiO2and SiO2ï¼›The main phase of Al₂O₃/Ti₃SiC₂composites isTi₃SiC₂and Al₂O₃，along with impurity phase TiC，and the oxidation product ofcomposites is TiO2and SiO2，includingAl₂O₃. What’s more，Al₂TiO₅with resistance tohigh temperature started forming while at1300℃.（2）Compared with the sample Ti₃SiC₂，Al₂O₃/Ti₃SiC₂composites showed bettermechanical properties，which was attributed to the additive of Al₂O₃resulting in theparticle-dispersing and the comprehensive energy absorption mechanisms of deflectionand pinning of crack. The fracture toughness and bending strength of Al₂O₃/Ti₃SiC₂composites reached maximum5.89MPa·m1/2and609MPa，while the additive amountof Al₂O₃was5%and20%，respectively.（3） The results of oxidation kinetics research showed that: Oxidation of eachsample obeyed parabolic law during the1100and1300℃. The parabolic rate constantsshowed that while the amount of additive of Al₂O₃was less than20%，the oxidationresistance of Al₂O₃/Ti₃SiC₂composites couldn’t be improved compared with sample T. In contrast，better high temperature oxidation resistance of Al₂O₃/Ti₃SiC₂composite canbe gotten when the content of Al₂O₃is increased further above20wt%.（4） Morphology of oxidation surface and cross-section of sample T and A20revealed that: Holes existed on the surface of the sample of A20accelerating theoxidation process，which made its oxidation resistance inferior to that of sample Tbelow1200℃. While the temperature increasedabove1200℃，sample A20showed abetter oxidation resistance due to the forming of new phase-Al₂TiO₅，which had a goodresistance to high temperature and thermalshock resistance，resulting in smaller valuesof thickness of oxidation scales.（5） The influence of content of Al₂O₃on oxidation resistance showed that: theoxidation resistance of Al₂O₃/Ti₃SiC₂composites was improved with increasing theamount of Al₂O₃. In order to get a better oxidation resistance than that of sample T，theamount of Al₂O₃couldn’t be less than20%.