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

Abstract

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.