Ti 3AlC 2-Al 2O 3-TiAl 3 composite fabricated by reactive melt infiltration

Abstract

Porous preforms were fabricated by cold-pressing process using powder mixture of TiC, TiO 2 and dextrin. After pyrolysis and sintering, Al melt was infiltrated into the porous preforms, leading to the formation of Ti 3AlC 2-Al 2O 3-TiAl 3 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 TiO 2 is reduced into Ti 2O 3 by carbon, the decomposition product of dextrin, which causes the spontaneous infiltration of Al melt into TiC/Ti 2O 3 preform. Then, Ti 3AlC 2-Al 2O 3-TiAl 3 composite is in-situ formed from the simultaneous reaction of Al melt with TiC and Ti 2O 3. 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 Ti 3AlC 2 grains and Al 2O 3 particles make the fracture toughness of TiAl 3 increase remarkably by various toughening mechanisms including stress-induced microcrack, crack deflection and crack bridging.