Fe/W扩散焊界面原子扩散行为分子动力学模拟

Molecular Dynamics Simulation of Atomic Diffusion Behavior at Fe/W Interface

为研究扩散焊工艺参数对Fe/W界面原子扩散行为的影响,建立了Fe(100)/W(100)界面结构模型。采用分子动力学(MD)方法模拟了1123~1323 K下Fe/W界面处原子扩散,观察具体扩散情况并计算扩散系数。结果表明:Fe/W界面呈现明显的非对称扩散现象,主要为W原子向Fe原子中扩散,且模拟时间越长该现象越明显。径向分布函数(RDF)说明Fe侧原子整体排列有序度高于W侧。根据原子均方位移(MSD)曲线拟合得出原子扩散系数和扩散激活能,在1123~1323 K温度下,Fe、W原子在Fe/W界面的扩散激活能分别为1.326 eV和0.84156 eV,W原子在Fe晶格中扩散势能低于Fe原子在W晶格中扩散势能,更容易突破能垒发生扩散。扩散温度和压力升高可有效提升界面扩散层厚度。一定程度上提高界面粗糙度有利于界面扩散层厚度增长,但粗糙度过大也会影响界面焊合。扩散系数基础数据可为实际工业生产中低活化钢与面向第一壁材料钨的扩散连接界面组织调控提供理论依据。

To investigate the effect of process parameters on the atomic diffusion behavior at the Fe/W interface,a low index crystal plane Fe(100)/W(100)interface structure model was established.Molecular dynamics(MD)method was used to simulate atomic diffusion at the Fe/W interface at 1123~1323 K,and the specific diffusion situation was observed and the diffusion coefficient was calculated.Results indicate that there is a significant asymmetric diffusion phenomenon at the Fe/W interface,mainly due to the diffusion of W atoms into Fe atoms,and the longer the simulation time,the more obvious this phenomenon becomes.The radial distribution function(RDF)indicates that the ordering degree on the Fe side is higher than that on the W side.According to the mean square displacement(MSD)curve fitting,the diffusion coefficient and diffusion activation energy were obtained.At temperatures of 1123~1323 K,the diffusion activation energies of Fe and W at the Fe/W interface were 1.326 and 0.84156 eV,respectively.The absolute value of the diffusion potential energy of W atom in Fe crystal is lower,making it easier to break through the energy barrier.The increasing of diffusion temperature and pressure can effectively increase the thickness of the interface diffusion layer.Increasing roughness of the interface to some extent is beneficial for increasing the thickness of the diffusion layer,but it also affects the interface closure.The basic data of diffusion coefficient can provide a theoretical basis for the microstructure control of diffusion bonding interface between low activation steel and tungsten facing the first wall material in actual industrial production.