| Summary: | 碩士 === 國立屏東科技大學 === 機械工程系所 === 99 === The temperatures of the β/α+β and Ms phase transition of the Ti-8Al-1V-1Mo alloy are in the range of 1020-1040℃ and 880-900℃, respectively. The purposes of the present studies are to investigate the annealed structures of the alloy by using of SEM, XRD, TEM and STEM-EDS equipments. The main results are described as following:
The microstructure of the alloy annealed at 1080℃ is essentially an (α'+α2) mixture lamellar-martensite structure. Some inter-phase IP1 belonging to HCP structure are formed on the α'/α' boundaries. During heated at 400℃ or 600℃, some β-phase and IP2-phase precipitates belonging to FCC structure are observed on α'/α' boundaries. Being annealed at 1000℃ below α/(α+β) transition about 30℃, the phase transitions in the α' region are similar to that observed of the 1080℃ specimens. And, annealed at 900℃ above Ms transition, some β-phase particles formed within the α-phase matrix and some IP2- phase precipitates are also observed on the α/β boundaries. In addition, during heated at 400℃, some ω-phase particles precipitate within the β matrix. In the meanwhile, being annealed at 900℃, a new W-phase precipitates with higher Mo and C elements are found. The lattice parameters of the W-phase can be identified to a=0.940 nm, b=c= 1.012nm. Annealed at 800℃below Ms transition, the microstructure of the alloy is essentially an (α+β) mixture bimodal structure. Some plate-like β-phase particles formed within α matrix and on the α/α boundaries. Some IP2-phase precipitates are also observed on the α/β boundaries. Moreover, based on the examination of STEM-EDS, it is imply that the cluster of Mo element and the diffusion of Si element will play an important roles on the inter-phase precipitates such as β-phase, IP1-phase and IP2-phase.
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