Microstructure evolution of directionally solidified Ti-45Al-8.5Nb-(W, B, Y) alloys |
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Authors: | XF DingJP Lin H QiLQ Zhang XP SongGL Chen |
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Affiliation: | State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China |
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Abstract: | Intermetallic Ti-45Al-8.5Nb-(W, B, Y) alloys were directionally solidified at constant growth rates (V) ranging from 10 to 400 μm/s under the temperature gradient G = 3.8 × 103 K/m. Quenching was performed at the end of directional solidification (DS) experiments. Microstructure evolution was investigated by analyzing the microstructures formed at the quenching interfaces and in the DS regions. The primary dendritic arm spacing (λ) decreases with increasing growth rate according to the relationship λ ∝ V−0.36. Both the width of columnar grain (λw) and the interlamellar spacing (λs) decrease with increasing growth rate according to the relationships λw∝V−1.13 and λs ∝ V−0.32, respectively. Lamellar microstructure initially disappears from the dendrites at the growth rate of 100 μm/s and subsequently from the interdendritic regions when the growth rate is up to 200 μm/s. The B2 particles can precipitate in the interdendritic regions. |
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Keywords: | Intermetallics Microstructure Directional solidification Crystal growth Segregation |
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