Microstructure and mechanical properties of TiAl3/Al2O3in situ composite by combustion process

Abstract

The microstructure and mechanical properties of TiAl3/Al2O3 in situ composite prepared via a combustion process were investigated in detail. Pure Al powder and TiO2 powder (molar ratio 13:3) were mechanically milled at 300 rpm for 18 ks. The milled powders were cold-pressed at 200 MPa for 0.3 ks and then green compact were sintered at 923-1173 K for 1.8 ks under Ar atmosphere. The micro structure of the sintered compact was analyzed using XRD, SEM and TEM/EDS, and the mechanical properties were evaluated using Vickers hardness and indentation fracture toughness tests. The compacts sintered at temperatures below 973 K consisted of a TiAl3 phase and remaining Al and TiO2 phases, while those sintered at temperatures above 1023 K consisted of a TiAl3 matrix, dispersed Al2O3 particles, and a plate-like Ti3Al phase. In addition, the compacts sintered above 1023 K had a higher hardness (approximately 800 Hv) compared to that of the TiAl3 single-phase compact (450 Hv). The fracture toughness of the TiAl3/Al2O3 composite was also approximately twice that of the TiAl3 single-phase compact. This improvement in the hardness and toughness is attributed to the microstructure of the composite, particularly the formation of dispersed Al2O3 particles and the Ti3Al plate-like phase in the TiAl3 matrix.