The ductility of TiAl intermetallics can be improved through stabilizing the ductile β phase.New β-stabilized Ti-45Al-xFe-yMo（x,y=1,2,3,4） alloys were designed through adding the β stabilizing elements Fe and Mo.The microstructural evolution and deformation behavior of the Ti-45Al-xFe-yMo alloys were investigated.The results show that the amount of β（B2） phase is increased with the increase of alloying elements.Mo shows a higher capability for stabilizing the β phase than Fe.In the optimized Ti-45Al-3Fe-2Mo alloy,the grains are significantly refined to about 12 μm,and this alloy shows a very good hot ductility at the elevated temperature.
The effect of carbon addition on the microstructures of TiAl-based alloy（Ti-45Al-3Fe-2Mo） was studied.The proportion of β/B2 phase reduces with the content of carbon increasing,while the colony size increases.With increasing the carbon content,the lamellar spacing first decreases from 267 nm（Ti-45Al-3Fe-2Mo） to 237 nm（Ti-45Al-3Fe-2Mo-0.3C） and 155 nm（Ti-45Al-3Fe-2Mo-0.5C）,but then increases to 230 nm（Ti-45Al-3Fe-2Mo-1.0C） with further increase in C level,which is affected by the inhibition of carbon atom and precipitation of carbides at the lamellar interface.Precipitation of carbides shows a response to aging time at 800 ℃.P-type carbides grow up at the boundaries and near the dislocation areas with the prolonging of aging time.And these carbides are projected different morphology in different beam directions（BD）.The effects of these microstructural modifications were examined and the observations were discussed.
Based on the analyses of the microstructures and phase diagrams of the TiAl-based alloy, the relationship among the composition, structure and mechanical properties of the B2-containing y-TiAI alloys was reviewed. The refinement of microstructures and improvement of mechanical properties of TiA1 alloy through stabilization of the β/B2 phase were reviewed. The mechanism of the superplastic behavior of the B2-containing y-TiAI alloys was discussed. With a reasonable addition of β-stabilizer, metastable B2 phase can be maintained, which is favorable for fine-grained structure and better high-temperature deformation behaviors. The mechanical properties of the B2-containing TiAI alloy, including the deformability and elevated temperature properties, can also be improved with doping elements and subsequent hot-working processes. The above mentioned researches discuss a new way for developing TiAI alloys with comprehensive properties, including good deformability and creep resistance.
