tastable spinodal decomposition L / L1 þ L2, where L1 is an Al- rich liquid phase and L2 is a Sn-rich liquid phase. The metastable miscibility gap for the AleSn system was thermodynamically esti- mated and can be found in Kim et al. [20] and in Mirkovic et al. [19]. The alloy studied in the present work, Al20Sn1Cu, is outside of the stable miscibility gap present in the ternary system. Thus, the microstructure observed in the BC and TR samples, would respond to the solidification pathway of the stable equilibrium phase dia- gram; that is without reaching the metastable miscibility gap.Kong et al. [22] studied the gas-atomised Al12Sn1Cu (wt.%) alloy. They also observed different kind of microstructures for different powder particles size. They found a dendritic and cellular a-Al matrix with Sn segregation at the a-Al grain boundaries for large powder particles and a microstructure of near-spherical small b-Sn particles in an a-Al matrix for small powder particles. More- over, they found that the size of the b-Sn particles decreased as the powder diameter decreased (i.e. cooling rate increased). The BC and TR samples from the present work and their large atomised powder particles developed the same kind of microstructure which sug- gests that had the same solidification pathway. The cooling rate was insufficient to undercool the material into the metastable misci- bility gap before the nucleation of the a-Al, and the liquid would adjust the composition by diffusion until rich the eutecticcomposition. Considering that is not clearly observed an eutectic microstructure at the a-Al grain boundaries, a divorced eutectic could occur due to both the Sn-rich eutectic composition and the cooling rate.Thus, the solidification pathway in those samples can be described as:L/a-AlþL/a-Alþb-SnPrecipitates of the q-Al2Cu intermetallic are also observed at the a-Al grain boundaries. Considering the maximum Cu solubility in b- Sn is in between 0.022 and 0.035 wt% [33,34] it is worth to suggest that the q-Al2Cu is segregated from the a-Al solid solution (maximum solubility in stable equilibrium is ~2.8wt%Cu and 0.05 wt%Cu at room temperature) [19].The melt-spun samples (SR) in the present work and small atomised powder particles in the Kong et al. [22] work show a microstructure characterized by rounded b-Sn particles embedded in an a-Al matrix. Similar observations were made by Kim et al. [20] in melt-spun ribbons of Al5Sn and Al10Sn (wt.%). They found that b-Sn particle size ranged from 1 mm to 50 nm depending on the wheel speed (from 9 m/s to 65 m/s) and the distance from the surface in contact with the wheel. This type of microstructure
tastable spinodal decomposition L / L1 þ L2, where L1 is an Al- rich liquid phase and L2 is a Sn-rich liquid phase. The metastable miscibility gap for the AleSn system was thermodynamically esti- mated and can be found in Kim et al. [20] and in Mirkovic et al. [19]. The alloy studied in the present work, Al20Sn1Cu, is outside of the stable miscibility gap present in the ternary system. Thus, the microstructure observed in the BC and TR samples, would respond to the solidification pathway of the stable equilibrium phase dia- gram; that is without reaching the metastable miscibility gap.Kong et al. [22] studied the gas-atomised Al12Sn1Cu (wt.%) alloy. They also observed different kind of microstructures for different powder particles size. They found a dendritic and cellular a-Al matrix with Sn segregation at the a-Al grain boundaries for large powder particles and a microstructure of near-spherical small b-Sn particles in an a-Al matrix for small powder particles. More- over, they found that the size of the b-Sn particles decreased as the powder diameter decreased (i.e. cooling rate increased). The BC and TR samples from the present work and their large atomised powder particles developed the same kind of microstructure which sug- gests that had the same solidification pathway. The cooling rate was insufficient to undercool the material into the metastable misci- bility gap before the nucleation of the a-Al, and the liquid would adjust the composition by diffusion until rich the eutecticcomposition. Considering that is not clearly observed an eutectic microstructure at the a-Al grain boundaries, a divorced eutectic could occur due to both the Sn-rich eutectic composition and the cooling rate.Thus, the solidification pathway in those samples can be described as:L/a-AlþL/a-Alþb-SnPrecipitates of the q-Al2Cu intermetallic are also observed at the a-Al grain boundaries. Considering the maximum Cu solubility in b- Sn is in between 0.022 and 0.035 wt% [33,34] it is worth to suggest that the q-Al2Cu is segregated from the a-Al solid solution (maximum solubility in stable equilibrium is ~2.8wt%Cu and 0.05 wt%Cu at room temperature) [19].The melt-spun samples (SR) in the present work and small atomised powder particles in the Kong et al. [22] work show a microstructure characterized by rounded b-Sn particles embedded in an a-Al matrix. Similar observations were made by Kim et al. [20] in melt-spun ribbons of Al5Sn and Al10Sn (wt.%). They found that b-Sn particle size ranged from 1 mm to 50 nm depending on the wheel speed (from 9 m/s to 65 m/s) and the distance from the surface in contact with the wheel. This type of microstructure<br>
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