【摘要】 在冷喷涂过程中,喷涂粒子被超音速气流加速到较高的速度,在低于喷涂材料熔点的温度下撞击基体,发生剧烈的塑性变形而沉积形成涂层.但是由于高速粒子碰撞变形的瞬时特点,不能对粒子变形沉积过程进行直接观察,通过对Ni团簇在Cu基体上的沉积过程的分子动力学模拟,可以观察到团簇撞击基体并在基体上沉积的过程,以及团簇和基体的形貌变化;另外,通过计算团簇原子进入基体表面层的数量探讨了影响团簇沉积过程的主要因素.更多还原

【Abstract】 Cold gas spray is a relatively new coating technique by which coatings can be formed without significant heating of the sprayed powder.In contrast to the conventional thermal spray processes,such as flame,arc,and plasma spraying,in cold spraying there is no melting of particles prior to impact on the substrate.In cold spray,particles are accelerated to a very high velocity by a flowing gas with supersonic speed and the temperature of spray particles is much lower than its melting point.However,being accomplished in so short an interval,the impact and deposition processes are difficult to be observed by experimental ways.Using molecular dynamics simulation,the deposition of nano-scale Ni clusters on Cu(001) surface was studied.The many-body potential is used to simulate the interatomic force between the atoms.By taking "snapshot",the impact,deposition process and the final appearances of the cluster and the substrate were observed directly.It is found that both the substrate and the cluster deform and lose the crystalline structure.But after reconstruction and relaxation,both of them recover the crystalline structure.In addition,the influence factors on deposition,such as incident velocity and the size of the cluster,are discussedr.Simulation results show that the higher incident velocity or the larger size of the cluster could result in stronger interaction between the substrate and the cluster owing to the higher kinetic energy of the cluster.更多还原