Formulation of Al–Bi–Sn immiscible alloys versus the solidification behaviors and structures
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In this work, the Al100−x(Bi45Sn55)x (x = 5, 15, 25 and 35) alloys with varied elemental compositions were prepared to understand the correlations of the elemental composition with the solidification behaviors and structures of the alloys. The results showed that the Sfh, Smc, S c-s 2 (Sn–Bi-rich, Al-rich) and S c-s 3 (Sn–Bi-rich, Al-rich, Sn–Bi-rich) structures were formed successively with the decreasing aluminum content, due to the increased aggregation degree of droplets. The increased aggregation resulted from (1) the increased width of the miscibility gap (from 0 to 146 K); (2) the increased volumetric fraction of the minority phase particles (from 8.91 to 49.98%); (3) the increased time of the L–LPS (from 0 to 0.46 s); (4) the decreased solidification rate (from 10.2 to 4.6 mm s−1). The exchange of core and shell occurred in as-cast Al–Bi–Sn immiscible alloys. The quantitative relationship between the composition and the collision probability of droplets was established to reveal the inner reasons for structural evolution. In addition, the hot-spot effect of the lower melting point droplets was responsible for the coarser monotectic structure around the lower melting point particles. The results from this work are a useful reference for regulating structural configuration of immiscible alloys via manipulating the composition.
This study was funded by the Strategic International Scientific and Technological Innovation Cooperation Special Funds of National Key R&D Program of China (2016YFE0204000) and the Program for Taishan Scholars of Shandong Province Government. This research was also supported by the National Natural Science Foundation of China (51471076, 51571102 and 51401085), the Shandong Natural Science Foundation (ZR2015BM018) and the Recruitment Program of Global Young Experts (Thousand Youth Talents Plan). Key Laboratory of Liquid Structure and Heredity of Materials of Shandong University are acknowledged for the technical assistance. We are indebted to Prof. Xiufang Bian, Prof. Xubo Qin, and Dr. Yanwen Bai for the help of viscosity and L-XRD tests and advice about the data processing and analysis.
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