Three-dimensional printing of nanolaminated Ti₃AlC₂ toughened TiAl₃-Al₂O₃ composites

Nanolaminates with a layered MN+1AXN crystal structure (with M: transition metal, A: group element, X: carbon or nitrogen, and N=1, 2, 3) offer great potential to toughen ceramic composites. A ternary Ti3AlC2 carbide containing ceramic composite was fabricated by three-dimensional printing of a TiC+TiO2 powder mixture and dextrin as a binder. Subsequent pressureless infiltration of the porous ceramic preform with an Al melt at 800°-1400°C in an inert atmosphere, followed by reaction of Al with TiC and TiO2 finally resulted in the formation of a dense multiphase composite of Ti3AlC2-TiAl3-Al2O3. A controlled flaw/strength technique was utilized to determine fracture resistance as a function of crack extension. Rising R-curve behavior with increasing crack extension was observed, confirming the operation of wake-toughening effects on the crack growth resistance. Observations of crack/microstructure interactions revealed that extensive crack deflection along the (0001) lamellar sheets of Ti3AlC2 was the mechanism responsible for the rising R-curve behavior.