Porous preforms were fabricated by cold-pressing process using powder mixture of TiC,TiO2 and dextrin.After pyrolysis and sintering,Al melt was infiltrated into the porous preforms,leading to the formation of Ti3AlC2-Al2O3-TiAl3 composite.Effects of cold-pressing pressure of preforms on microstructures and mechanical properties of the composites were studied.Synthesis mechanism and toughening mechanism of composite were also analyzed.The results shows that TiO2 is reduced into Ti2O3 by carbon,the decomposition product of dextrin,which causes the spontaneous infiltration of Al melt into TiC/Ti2O3 preform.Then, Ti3AlC2-Al2O3-TiAl3 composite is in-situ formed from the simultaneous reaction of Al melt with TiC and Ti2O3.With the increase of cold-pressing pressure from 10 MPa to 40 MPa,the pore size distribution of the preforms becomes increasingly uniform after pre-sintering,which results in the reduction of defects,and the decrease of property discrepancy of composites.Nano-laminated Ti3AlC2 grains and Al2O3 particles make the fracture toughness of TiAl3 increase remarkably by various toughening mechanisms including stress-induced microcrack,crack deflection and crack bridging.
