Abstract
Directionally solidified microstructures of Ni-24.19wt% Nb hypereutectic alloy were investigated at the growth rate of 10 μm/s, and the abruptly decreasing growth rate from 10 to 1 μm/s. The results show that the microstructure consists of Ni3Nb primary phase and eutectic (Ni + Ni3Nb), in agreement with the theoretical calculation results at the growth rate of 10 μm/s. After the solidified distance of 20 mm, the growth of Ni3Nb primary phase achieves the quasi-steady state. At the abruptly decreasing growth rate from 10 to 1 μm/s, the volume fraction of Ni, Nb primary phase firstly increases, attributing to the change of interface composition, and then decreases to zero. Finally, the off-coupled growth microstructure changes to the coupled growth eutectic due to the competitive growth of interface temperature between Ni3Nb primary phase and eutectic (Ni + Ni3Nb). The disappearance of Ni3Nb primary phase does not simultaneously occur and mainly originates from the side to the center of the sample.
Original language | English |
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Pages (from-to) | 35-40 |
Number of pages | 6 |
Journal | Hangkong Cailiao Xuebao/Journal of Aeronautical Materials |
Volume | 26 |
Issue number | 3 |
State | Published - Jun 2006 |
Keywords
- Competitive growth
- Directional solidification
- Ni-Nb eutectic alloy