Abstract
To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb (at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated. The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 µm∙s-1 under the temperature gradients of 15-20 K∙mm-1, and the primary phase is transformed into an α phase at relatively higher growth rates (V >20 µm∙s-1). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 µm∙s-1 under a temperature gradient of 15 K∙mm-1. The increase of temperature gradient to 20 K∙mm-1 can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as \(L\xrightarrow{{L \to \beta }}L + \beta \xrightarrow{{L + \beta \to \alpha }}\alpha + {\beta _R}\xrightarrow{{\beta \to \alpha }}\alpha \xrightarrow{{\alpha \to \gamma }}\alpha + \gamma \xrightarrow{{\alpha \to {\alpha _2} + \gamma }}{\gamma _R} + \left( {{\alpha _2} + \gamma } \right)\), in which βR and γR mean the residual β and γ
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Male, born in 1969, Ph.D., Professor, His research mainly focuses on the solidification processing of nonferrous alloys. He has published more than 300 papers and has been awarded 22 invention patents of China.
This research was financially supported by the National Natural Science Foundation of China (Nos. 51331005 and 51425402).
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Luo, Ls., Liu, T., Li, K. et al. Microstructures, micro-segregation and solidification path of directionally solidified Ti-45Al-5Nb alloy. China Foundry 13, 107–113 (2016). https://doi.org/10.1007/s41230-016-6004-z
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DOI: https://doi.org/10.1007/s41230-016-6004-z