Ti5Si3 whisker in-situ reinforced TiAl alloys

The effects of Fe, Cr, V, and Nb on the microstructures, tensile properties at 20 degreesC and 900 degreesC, and creep resistance at 800 degreesC of Ti5Si3 whisker-reinforced Ti52Al48-3Si2M alloys were investigated. The addition of Fe, Cr, Nb. and V modifies not only the morphologies but also the distribution of Ti5Si3 whiskers. A microstructure with a uniform and homogeneous distribution of Ti5Si3 whiskers was obtained in a Ti52Al48-3Si2Cr2V alloy by conventional ingot metallurgy. The Ti52Al48-3Si2Cr2V alloy has the best room-temperature tensile strength, relatively good ductility, an attractive tensile property at 900 degreesC, and good creep resistance at 800 degreesC. The improvement of properties results from not only the homogeneous distribution of Ti5Si3 whiskers but also from the higher fracture strength of the Ti5Si3 whisker and the interface property. The solubility of V in the Ti5Si3 phase is higher than that of Fe, Cr, and Nb. The element V is very effective in strengthening the Ti5Si3 whiskers. Different failure modes were found in the Ti5Si3 whisker-reinforced TiAl alloys at room temperature. Cleavage fracture dominates the failure of Ti5Si3 whiskers and gamma phase in V-free alloys, whereas crack deflection and branching at the Ti5Si3-whiskerly-matrix interface, subsequently followed by interface debonding and whisker bridging, were observed in Ti52Al48-3Si2V and Ti52Al48-3Si2Cr2V alloys. In addition, twinning and dislocation slip in Ti5Si3 whisker-reinforced TiAl alloys were investigated.