摘要
In order to understand the influence of supergravity on the microstructure of materials,crystal nucleation,dendritic growth,and polycrystal solidification under supergravity are investigated by using the modified nucleation theory and phase field models.Firstly,supergravity is considered in the nucleation theory by using pressure-dependent Gibbs free energy.It is found that the critical radius decreases and the nucleation rate increases when supergravity rises.Secondly,anisotropic heat transport is proposed in the phase field model to investigate the influence of supergravity on dendritic growth.Phase field simulations show that supergravity promotes the secondary dendritic growth in the direction parallel to supergravity.Finally,a multiply phase field model with pressure-dependent interfacial energy is employed to simulate the polycrystalline solidification under supergravity.Due to the depth-dependent pressure by supergravity,crystal grains are significantly refined by high pressure.In addition,gradient distribution of grain size is obtained in the solidification morphology of polycrystalline,which is consistent with previous experimental observations.Results of this work suggest that supergravity can be used to tune the microstructures and properties of materials.
超重力场对材料的微结构具有显著影响,为探究其影响机理,我们对经典形核理论与凝固模型进行了修正,并运用相场法模拟了单晶和多晶的凝固过程.将与超重力系数相关的吉布斯自由能引入初始形核中,发现随着超重力系数的增加,临界形核半径减小,临界形核率显著增加.基于超重力场促进对流换热的实验结果,我们提出了各向异性热传导的单晶生长模型,发现超重力场有利于该方向二次枝晶的生长.最后,将超重力对初始形核分布的影响包含到多晶凝固模型中,模拟发现随着超重力系数的增大,晶粒尺寸发生明显细化,并在超重力方向形成梯度分布,与实验观察吻合较好.本文结果表明,利用超重力场能够调控晶粒尺寸的分布,可以作为调控材料特殊微结构与性能的新方法.
作者
Zhenhua Zhang
Xu Hou
Yong Zhang
Hua Wei
Jie Wang
张振华;侯旭;张勇;韦华;王杰(Department of Engineering Mechanics,School of Aeronautics and Astronautics,Zhejiang University,Hangzhou,310027,China;Zhejiang Laboratory,Hangzhou,311100,China;Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province,Zhejiang University,Hangzhou,310027,China;Center for Hypergravity Experimental and Interdisciplinary Research,Zhejiang University,Hangzhou,310058,China)
基金
This work was supported by the Basic Science Center Program for Multiphase Evolution in Hypergravity of the National Natural Science Foundation of China(Grant No.51988101)
the National Natural Science Foundation of China(Grant Nos.12192214 and 11972320)
the Key Research Project of Zhejiang Laboratory(Grant No.2021PE0AC02).
