Microstructures of PM Ti-45Al-10Nb alloy fabricated by reactive sintering
(1. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
2. School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China)
2. School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040, China)
Abstract: Powder metallurgy Ti-45Al-10Nb alloys was successfully fabricated by reactive sintering of milled powders at 1350 °C for 2 h in vacuum. The microstructure, in particular, constituent phases, grain size, precipitates of the product was investigated in detail. The results indicate that a double phase γ+α2 microstructure containing Ti2AlC precipitate is obtained under the sintering condition, and the alloy exhibits a fine and homogenous microstructure compared with traditional TiAl base. In fine grain structure, the average grain sizes for the γ and α2 phases are (2.3±0.05) and (5.6±0.05) μm, respectively. Additionally, numerous dislocations are observed in the alloy, and the dislocation density in γ phase is significantly higher than that in α2 phase. The formation mechanisms of the dislocation in the present alloy were also discussed in detail.
Key words: high Nb-TiAl alloy; powder metallurgy; microstructure; dislocation