Effect of TiB, TiC and Y₂O₃ on tensile properties and creep behavior at 650 ℃ of titanium matrix composites

Two kinds of (TiB + TiC + Y₂O₃)/α-Ti composites with different TiB and TiC contents and the corresponding matrix alloy were prepared by induction skull melting. The results showed that the matrix alloy possessed a typical widmanstatten structure while the composites displayed a basket-weave structure characterized by α lamellae with different orientations. Obvious TiB/TiC structures were observed with the increase of reinforcements, which were very stable in the tensile and creep processes at high temperature. The ultimate tensile strength at 650 ℃ increased from 589 MPa to 730 MPa and 812 MPa with the increase of reinforcements. The enhancement in strength of the composites was elucidated on the load transfer strengthening of the reinforcements. The creep properties of the composites at 650 ℃ have been significantly improved due to the impediment of reinforcements and silicides to dislocation movement. The strengthening effect increased with the increase of reinforcements and stress. At 650 ℃/290 MPa, compared with the matrix alloy, the creep life of composite with highest reinforcements content was increased by 931% and the steady-state creep rate was reduced by 93%. According to the different stress levels, the composites exhibited different creep behaviors. At 230 MPa, the sub-grains were obvious and the number of actuated dislocations is small. At 290 MPa, the dislocation pile-up was serious and the obviously coarsened silicides lost their pinning effect.