钛/铝爆炸焊接界面扩散行为分子动力学模拟

Molecular Dynamics Simulation of Diffusion Behavior of Ti/Al Explosive Welding Interface

摘要:

为揭示钛/铝爆炸焊接界面原子的扩散行为，采用分子动力学模拟从原子尺度分析了钛/铝爆炸焊接界面原子的微观扩散机理。利用Materials Studio建立了钛/铝爆炸焊接焊点处的分子动力学模型，结合爆炸焊接的物理过程，将爆炸焊接过程分为加载和卸载2个阶段，通过LAMMPS程序计算了爆炸焊接钛、铝原子的均方位移、径向分布函数、扩散层厚度等，利用OVITO软件再现了不同阶段界面原子的扩散行为。在爆炸焊接加载阶段，钛、铝原子不发生扩散，只在平衡位置做振动，铝原子振动要比钛原子振动强。爆炸焊接卸载开始时，钛、铝原子发生互扩散。钛/钛原子键能高，不易破坏，铝/铝原子键能低，容易破坏产生空位、间隙等缺陷，有利于钛原子深入扩散到铝晶格内部，但铝原子难以进入钛的晶格内部。采用扫描电镜和EDS能谱表征了钛/铝爆炸焊接复合材料界面元素分布，与模拟结果有很好的一致性。

Abstract:

In order to reveal the diffusion behavior of Ti/Al interface, the molecular dynamics simulation was applied to study the microscopic diffusion mechanisms of Ti/Al explosive welding interface at the atomic scale. Molecular dynamics model of Ti/Al explosive welding spot was established by Materials Studio (MS). According to the physical process of explosive welding, the simulation of the collision was divided into two stages: the loading stage and the unloading stage. The mean square displacement (MSD), radial distribution function (RDF), and diffusion layer thickness were calculated by LAMMPS, and the diffusion behavior of interfacial atoms at different stages was reproduced by OVITO. Results show that in the loading stage of explosive welding, Ti and Al atoms do not diffuse but only vibrate at the equilibrium position, and the vibration of Al atoms is stronger than that of Ti atoms. The atomic diffusion only occurs in the unloading stage of the explosive welding process. The Ti-Ti bonding energy is too high to break. The Al-Al bonding energy is low, so it is easy to be damaged, resulting in vacancies, gaps and other defects, which promotes the deep diffusion of Ti atoms into the Al substrate lattice while hindering Al atoms from entering the Ti substrate lattice. The simulation result is basically in accordance with EDS experimental result.