A triple comparative study of primary dendrite growth and peritectic solidification mechanism for undercooled liquid Fe59Ti41 alloy
A triple comparative study of primary dendrite growth and peritectic solidification mechanism for undercooled liquid Fe59Ti41 alloy
复制标题
DOI：
10.1016/j.actamat.2017.03.019
复制
发表时间：
2017-05
期刊：
影响因子：
9.4
通讯作者：
Y. H. Wu;J. Chang;Wen Wang;L. Hu;S. J. Yang;B. Wei
中科院分区：
文献类型：
--
作者：
Y. H. Wu;J. Chang;Wen Wang;L. Hu;S. J. Yang;B. Wei
采用静电悬浮（ESL）和电磁悬浮（EML）方法结合高速摄影技术定量研究了过冷亚包晶Fe59Ti41合金的快速凝固动力学。通过 ESL 和 EML 方法获得的最大过冷度 Δ 分别为 200 K (0.12TL) 和 315 K (0.19TL)。在不同的过冷度下记录了对应于初级枝晶生长和随后的包晶反应的双重辉过程。一次枝晶生长速度V与过冷度ΔT的关系满足双指数关系。在约 86 K 的相同临界过冷度下，实验确定了包晶反应的最长孵育时间和最高过冷度。相反，包晶反应时间随着 ΔT 的增加而线性减少。在ESL和EML实验中，随着ΔTris的变化，初生Fe2Ti相依次出现为轮廓分明的粗大枝晶、高度细化的枝晶，最后演变成由蠕虫状枝晶组成的迷宫状形貌。同时，包晶FeTi相的层厚和体积分数显着减小，这表明包晶反应在一定程度上受到抑制。 Fe2Ti 和 FeTi 相的固溶度在快速凝固过程中显着扩展。作为另一个比较，还进行了落管实验，以探讨较大过冷度和冷却速率下的凝固行为。随着合金液滴尺寸的减小，观察到“包晶凝固→初生相和包晶相之间的亚稳态耦合生长”的机制转变。
The rapid solidification kinetics of undercooled hypoperitectic Fe59Ti41alloy was quantitatively investigated by electrostatic levitation (ESL) and electromagnetic levitation (EML) methods combined with a high-speed photography technique. The maximum undercoolings ΔTobtained by ESL and EML methods were 200 K (0.12TL) and 315 K (0.19TL), respectively. Double recalescence processes corresponding to the primary dendrite growth and subsequent peritectic reaction were recorded at various undercoolings. The dependence of primary dendrite growth velocityVon the undercooling ΔTsatisfied a double-exponential relation. A longest incubation time and a highest undercooling of peritectic reaction were experimentally determined at the same critical undercooling of about 86 K. In contrast, the peritectic reaction time decreased linearly with enhanced ΔT. As ΔTrised in ESL and EML experiments, primary Fe2Ti phase successively appeared as well-defined coarse dendrites, greatly refined dendrites and finally evolved into a maze-like morphology composed of vermicular dendrites. Meanwhile, the layer thickness and volume fraction of peritectic FeTi phase remarkably reduced, which suggested that peritectic reaction was suppressed to some extent. The solid solubilities of Fe2Ti and FeTi phases were significantly extended during rapid solidification. As another comparison, drop tube experiment was also conducted to explore the solidification behaviors under larger undercoolings and cooling rates. A mechanism transition of ‘peritectic solidification → metastable coupled-growth between primary and peritectic phases’ was observed with decreasing alloy droplet size.