Extraordinary Solidification Mechanism of Liquid Alloys Under Acoustic Levitation State
Extraordinary Solidification Mechanism of Liquid Alloys Under Acoustic Levitation State
复制标题
声悬浮态液态合金的非凡凝固机制
DOI：
10.1002/adma.202206464
复制
发表时间：
2022-11-18
影响因子：
29.4
通讯作者：
Wei, Bingbo
中科院分区：
文献类型：
--
作者：
Geng, Delu;Yan, Na;Wei, Bingbo
利用高强度超声可以实现各种材料的声悬浮，为空间模拟条件下的材料加工提供了自由表面和无容器状态。声辐射压力、声流和超声空化等非线性效应为调节液体材料的流体动力学和凝固机制开辟了特殊的途径。本文全面探讨了声悬浮液滴内的液体流动、过冷性、相分离、晶体成核和生长等物理特性，揭示了液态合金的异常凝固动力学。超声振幅调制后，水滴的2 ~ 10阶扇形振荡伴随内部势流，超声强度的增强促进了冰核的形成，从而减少了水的过冷。非混相Al-Cu-Sn合金相分离过程中富锡微球的迁移主要受声悬浮引起的微滴变形和旋转影响。在声悬浮过程中，液态Ag - cu - ge和Ni - sn合金的高过冷态导致（Ag）枝晶的细化和反常（Ni+Ni3Sn）共晶的形成。超声-液体相互作用在Ag-Cu和Ni-Sn共晶合金无容器凝固过程中也会产生表面波。
The acoustic levitation of various materials can be realized by highly intensive ultrasound, which provides a free surface and containerless state for materials processing under space simulation conditions. The nonlinear effects such as acoustic radiation pressure, acoustic streaming, and ultrasonic cavitation open up special access to modulate the fluid dynamics and solidification mechanisms of liquid materials. Here, the physical characteristics of liquid flow, undercooling capability, phase separation, and crystal nucleation and growth within acoustically levitated droplets are explored comprehensively to reveal the extraordinary solidification kinetics of liquid alloys. The sectorial shape oscillations of the 2nd to 10th order modes accompanying internal potential flow are observed for water droplets with modulated ultrasound amplitudes, while the enhanced ultrasound intensity promotes ice nucleation and thus reduces water undercooling. The migration of Sn‐rich globules during phase separation of immiscible Al–Cu–Sn alloy is dominated by the droplet deformation and rotation related to acoustic levitation. The high undercooling states of liquid Ag–Cu–Ge and Ni–Sn alloys during acoustic levitation result in the refinement of (Ag) dendrites and the formation of anomalous (Ni+Ni3Sn) eutectics. The ultrasound–liquid interaction also induces surface waves during the containerless solidification of Ag–Cu and Ni–Sn eutectic alloys.