Microstructure and Mechanical Properties of TiAl3/Al2O3 in situ Composite by Combustion Process

The microstructure and mechanical properties of TiAl3/Al2O3 in situ composite by combustion process are investigated in details. Pure Al powder and TiO2 powder were mechanically milled with a molar ratio of 13 : 3 at 300 rpm for 18 ks. This milling powder's green compact cold-pressed at 200 MPa for 0.3 ks sintered at 923 to 1173 K for 1.8 ks under Ar atmosphere. The microstructure of the sintered compact was identified by XRD, SEM and TEM/EDS. Mechanical properties were evaluated by Vickers hardness and indentation fracture toughness tests. The compacts at less than 973 K consist of a TiAl3 phase and remained phases of Al and TiO2, while the compact at more than 1023 K consist of TiAl3 matrix, dispersed Al2O3 particles and some plate like Ti3Al phase. The compacts at more than 1023 K have the higher hardness around 800 Hv compared to TiAl3 single phase compact with 450 Hv. The fracture toughness of TiAl3/Al2O3 composite is about two times TiAl3 single phase compact. This improvement of hardness and toughness is attributed to the effect of the microstructure formation of dispersed Al2O3 particles and Ti3Al plate like phase in the TiAl3 matrix.