Abstract To prepare high-purity Ti–Si alloys, we newly used vacuum directional solidification technology to purify and separate Ti–Si alloys, which have different compositions (Ti-8.45 wt%Si, Ti-63.7 wt%Si, Ti-71.6 wt%Si, and Ti-84.1%wt%Si). The pulling-down rates in the directional solidification were to be 3 μm/s, 5 μm/s, and 7 μm/s, respectively, to investigate their effects on the purification. The results showed that vacuum directional solidification can purify Ti–Si alloys efficiently without discharging waste acid, slag and gas, and the slower pulling-down rate could result in better purification results. The impurities, Fe, Al, V, and Ni, could be removed due to their segregation behavior on the boundary of the solid and liquid phases. However, the impurities Ca and Mg could be removed using the vacuum technology because their vapor pressures were significantly higher than those of Si and Ti. TiSi2 could be precipitated and separated from the Ti-63.7 wt%Si and Ti-71.6 wt%Si alloys. The precipitated TiSi2 could be agglomerated at the bottom of the Ti–Si alloys, under the effect of gravity. The phases in the Ti–Si alloys, after vacuum directional solidification, were observed and determined using an electron probe micro-analyzer (EPMA). The results showed that the eutectic Ti-8.45 wt%Si alloy consisted of Ti5Si3 and Ti, the Ti-63.7 wt%Si and Ti-71.6 wt%Si alloys consisted of TiSi2 and eutectic Si–Ti alloy at the Si-rich side, and the Ti-84.1 wt%Si alloy consisted of Si particles and eutectic Si–Ti alloy at the Si-rich side. The study shows that vacuum directional solidification is an efficient and clean technology for the purification of Ti–Si alloys, and for the preparation of TiSi2 through the separation of Ti–Si alloys.

中文翻译：

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真空定向凝固制备高纯钛硅合金

摘要 为了制备高纯度 Ti-Si 合金，我们新使用真空定向凝固技术来纯化和分离具有不同成分的 Ti-Si 合金（Ti-8.45 wt%Si、Ti-63.7 wt%Si、Ti-71.6 wt%Si %Si 和 Ti-84.1%wt%Si)。定向凝固中的下拉速率分别为 3 μm/s、5 μm/s 和 7 μm/s，以研究它们对纯化的影响。结果表明，真空定向凝固可以在不排放废酸、废渣和废气的情况下有效净化Ti-Si合金，并且较慢的下拉速度可以获得更好的净化效果。杂质 Fe、Al、V 和 Ni 由于它们在固液相边界上的偏析行为可以被去除。然而，杂质 Ca 和 Mg 可以使用真空技术去除，因为它们的蒸气压明显高于 Si 和 Ti。TiSi2 可以从 Ti-63.7 wt%Si 和 Ti-71.6 wt%Si 合金中沉淀和分离。在重力作用下，析出的 TiSi2 可以聚集在 Ti-Si 合金的底部。在真空定向凝固后，Ti-Si 合金中的相使用电子探针显微分析仪 (EPMA) 进行观察和测定。结果表明，共晶 Ti-8.45 wt%Si 合金由 Ti5Si3 和 Ti 组成，Ti-63.7 wt%Si 和 Ti-71.6 wt%Si 合金由 TiSi2 和富硅侧的共晶 Si-Ti 合金组成， Ti-84.1 wt%Si 合金由 Si 颗粒和富硅侧的共晶 Si-Ti 合金组成。