Macrosegregation and thermosolutal convection-related freckle formation in directionally solidified Sn-Ni peritectic alloy in crucibles with different diameters
(1. School of Materials and Energy, Lanzhou University, Lanzhou 730000, China;
2. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China;
3. Northwest Rare Metal Materials Research Institute, Shizuishan 753000, China)
2. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China;
3. Northwest Rare Metal Materials Research Institute, Shizuishan 753000, China)
Abstract: Different from other alloys, the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn-Ni peritectic alloys. In addition, the experimental results demonstrate that the dendritic morphology is influenced by the temperature gradient zone melting and Gibbs-Thomson effects. A new Rayleigh number (RaP) is proposed in consideration of both effects and peritectic reaction. The prediction of RaP confirms the freckle formation in two regions during peritectic solidification. Besides, heavier thermosolutal convection in samples with larger diameter is also demonstrated.
Key words: freckle formation; directional solidification; thermosolutal convection; dendritic solidification; Sn-Ni peritectic alloy