三元复相合金熔体的涡旋场声悬浮和凝固过程机理研究

Vortex-field acoustic levitation can simultaneously provide three supernormal solidification conditions of containerless environment, vortex stirring and ultrasonic effects, while the solidification mechanisms of liquid alloys under supernormal solidification conditions are the important research subjects of materials science. This proposal plans to develop vortex-field acoustic levitation technique and investigate the solidification mechanisms of liquid ternary Al-Cu-Si/Sn multiphase alloys under vortex-field acoustic levitation condition. The main research contents and aims are (i) studying the principle and active control method of vortex-field acoustic levitation to stably levitate liquid alloys; (ii) researching the law of movement, heat transfer and mass transfer of liquid alloys to learn the effects of acoustic vortices on liquid alloys; (iii) investigating the solidification processes and microstructures of Al-Cu-Si/Sn ternary eutectic and monotectic alloys to discover the mechanisms of competitive nucleation and cooperative growth, and the mechanisms of liquid phase separation under vortex-field acoustic levitation condition; (iv) simulating the solidification processes of liquid ternary multiphase alloys by using multiphase-field models to elucidate the formation mechanisms of microstructures and build the theoretical solidification model of ternary multiphase alloys under vortex-field acoustic levitation condition.

涡旋场声悬浮方法可同时提供无容器环境、涡流搅拌和超声作用三种超常条件，而液态合金在超常条件下的凝固规律是材料科学的重要研究课题。本项目以三元Al-Cu-Si/Sn复相合金为研究对象，发展涡旋场声悬浮无容器处理技术，结合激光加热和高速摄像等实验技术，研究涡旋场声悬浮条件下合金熔体的凝固过程机理。重点研究合金熔体的涡旋场声悬浮及其主动控制方法，实现金属材料在涡旋场声悬浮条件下的熔化和凝固。研究涡旋场声悬浮条件下合金熔体的运动规律及传热传质特点，阐明涡旋声场对合金熔体的作用机制。揭示涡旋场声悬浮条件下三元共晶竞争形核和协同生长机制以及三元偏晶合金的液相分离机制。通过多元多相相场模拟研究，阐明涡旋场声悬浮条件下三元复相合金的凝固组织形成规律，建立涡旋场声悬浮条件下三元复相合金的凝固过程理论模型。

涡旋场声悬浮是一种很有潜力的材料无容器处理方法，但目前涡旋场声悬浮只能处理低密度材料。本项目在环形声源阵列涡旋场声悬浮技术的基础上系统研究了管道约束环形声源阵列涡旋场声悬浮技术，得到了其最佳悬浮性能与几何参数的关系，通过优化设计首次利用涡旋声场成功悬浮了高密度材料钢、铜、铱等。采用该技术我们深入研究了固体和液体在涡旋声场中的运动和变形规律，发现涡旋声场携带的轨道角动量转移可以驱动被悬浮固体高速旋转(达6500rps)，驱动液体内部产生涡流。超声振动作用可以使AlCu合金凝固组织细化，硬度和电导率性能提高。激光加热会引起涡旋场势阱和声悬浮力的突变从而导致被悬浮样品失稳，涡旋+驻波耦合场是实现激光加热金属材料无容器处理的潜在理想声悬浮方法。