Abstract: TiAl-based alloys with various compositions (includingTi-48Al, Ti-47Al-2Cr-2Nb, Ti-47Al-2Cr-2Nb-0.2B and Ti-47Al-3Cr, in mole fraction) had been prepared by elemental powder metallurgy (EPM). The results have shown that the density of the prepared Ti-48Al alloy increases with increasing hot pressing temperature up to 1300 degreesC. The Ti-48Al alloy microstructure mainly consisted of island-like Ti3Al phase and TiAl matrix at hot pressing temperature below 1300 degreesC, however, coarse alpha (2)/gamma lamellar colonies and gamma grains appeared at 1400 degreesC. It has also indicated that the additions of elemental Cr and B can refine the alloy microstructure. The main microstructural inhomogeneity in EPM TiAl-based alloys was the island-like aa phase or the aggregate of alpha (2)/gamma lame[[ar colony, and such island-like structure will be inherited during subsequent heat treatment in (alpha+gamma) field. Only after heat treatment in a field would this structure be eliminated. The mechanical properties of EPM TiAl-based alloys with various compositions were tested, and the effect of alloy elements on the mechanical properties was closely related to that of alloy elements on the alloy microstructures. Based on the above results, TiAl-based alloy exhaust valves were fabricated by elemental powder metallurgy and diffusion joining. The automobile engine test had demonstrated that the performance of the manufactured valves was very promising for engine service.

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