Microstructures and mechanical properties of (Ti,Cr)Al/Al2O3 composites fabricated by reactive hot pressing from Ti, Al and Cr2O3

Titanium aluminide composites reinforced with in situ formed Al2O3 were fabricated by a reactive hot press method, using Cr2O3, Al and Ti powders as raw materials. The effect of Cr2O3 addition on the microstructures and mechanical properties of the (Ti,Cr)Al/Al2O3 composite was characterized. The results show that the TiAl matrix is refined gradually with increasing the amount of Cr2O3. The Vickers-hardness and densities of the (Ti,Cr)Al/Al2O3 composite increase gradually with increasing Cr2O3 content. When the Cr2O3 content is 4.47 wt.%, the compressive strength, flexural strength and fracture toughness of the composite reach the maximum values of 1032 MPa, 634 MPa and 9.78 MPa m1/2, which are substantially higher than those of the monolithic TiAl based alloy by about 18%, 78% and 80.5%, respectively. The increase in mechanical properties for the (Ti,Cr)Al/Al2O3 composite is due to the toughening effect arising from the combination of Cr solid solution in TiAl matrix and in situ formed Al2O3.