Al-Ag-Ge合金熔凝过程中液相流动机制与旋涡组织形成的相关规律研究  

Fluid flow and vortex-shaped structure formation mechanisms of Al-Ag-Ge alloy

作　　者：李浩然[1] 阮莹[1] 魏炳波[1] LI HaoRan;RUAN Ying;WEI BingBo(School of Physical Science and Technology,Northwestern Polytechnical University,Xi’an 710072,China)

机构地区：[1]西北工业大学物理科学与技术学院,西安710072

出　　处：《中国科学：技术科学》2022年第6期941-956,共16页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:U1806219,52073232,52088101);陕西省杰出青年科学基金(编号:2020JC-11);陕西省科技创新团队项目(编号:2021TD-14)资助。

摘　　要：采用电磁悬浮、感应熔炼、电弧熔炼和电阻熔炼等四种实验技术,并结合有限元数值模拟方法,系统地研究了Al_(70)Ag_(20)Ge_(10)合金的液相流动规律与凝固机制.与常规慢速凝固情况不同,Al_(70)Ag_(20)Ge_(10)合金在这四种实验条件下均能形成一种特殊的旋涡状凝固组织,旋涡组织的形成受到凝固前熔体内的液相流动与冷却速率的影响.在电磁悬浮与感应熔炼过程中洛伦兹力驱动熔体内的湍流流动,电弧熔炼过程中的湍流流动主要由电弧力引起,在电阻熔炼方式中则受表面张力与浮力驱动引起熔体内的层流流动.在快速流动的作用下,Ag_(2)Al相领先于近平衡条件下的(Al)相首先形核并以亚稳的旋涡状枝晶形态生长,在生长过程中保留了合金熔体的流场运动形态.当冷却速率增加时亚稳Ag_(2)Al枝晶快速生长,凝固组织中的旋涡密度随之增加.随流场驱动力增强,亚稳Ag_(2)Al枝晶生长的曲率半径减小,旋涡组织中各相之间的竞争形核与生长更加显著,最终旋涡组织内部完全形成不规则(Al)+Ag_(2)Al+(Ge)三相共晶.Fluid flow and solidification mechanisms of Al_(70)Ag_(20)Ge_(10) alloy were systematically investigated using electromagnetic levitation,induction,arc,and resistance melting techniques coupled with finite element simulation method.A unique type of vortex-shaped microstructure was formed in these four experiments.This was different from the result under slow solidification conditions.The formation of the vortex-shaped structure was affected by fluid flow and cooling rate of alloy melt.The Lorentz force caused turbulent flow in alloy melt,while the turbulent flow during arc melting was driven by arc force under electromagnetic levitation or induction melting conditions.The surface tension and buoyancy force caused laminar flow in alloy melt during the resistance melting process.Due to rapid flow,the Ag_(2)Al phase nucleated ahead of the Al phase,primarily under near-equilibrium conditions.The metastable Ag_(2)Al dendrites grew as vortex-shaped morphology and preserved the melt flow pattern during solidification.The increased cooling rate caused a rapid growth of metastable Ag_(2)Al dendrites with increased vortex density.The curvature radius of metastable Ag_(2)Al dendrites decreased with enhanced melt flow;meanwhile,the more drastic nucleation and growing competition among phases occurred.Finally,irregular Al,Ag_(2)Al,and Ge ternary eutectics fully formed inside the vortex-shaped structure.

关 键 词：液相流动 冷却速率 共晶 快速凝固 凝固组织 

分 类 号：TG146.21[一般工业技术—材料科学与工程]