温度及深度对钛中氦泡释放过程影响的分子动力学研究

A molecular dynamics study of temperature and depth effect on helium bubble released from Ti surface

利用分子动力学模拟方法对温度及He泡深度给金属Ti内He泡的体积、压强和释放过程等带来的影响进行了研究.首先,通过研究室温下He泡在金属Ti内不同深度处的状态,得到He泡的形状、压强、体积等物理量随其深度的变化规律.发现He泡压强随其深度增加逐渐变大,体积则逐渐减小,但当He泡深度增大到2.6 nm时,二者均维持在某个固定值附近.然后对包含有He泡的Ti体系在温度作用下的演化过程进行了模拟,发现不同深度处He泡从金属Ti内释放出来所需要的临界温度有很大差别,总体来看He泡越深,释放所需的临界温度越高.但不同温度下He原子的释放速率没有明显差别,释放过程几乎均为瞬间完成.最后通过对He泡内部压强和其上方金属Ti薄层的抗张强度进行统计对比,阐述了金属Ti体内He泡的释放机制:当He泡内部压强大于其上方Ti薄层抗张强度时,He泡就会将Ti薄层撕裂,从而使He原子得到释放.

Using molecular dynamics simulation, the effects of temperature and depth of helium bubble on volume, pressure and releasing process of helium bubble in metal Ti are investigated. First, through studying the states of helium bubble at different depths at room temperature, the variation regularities of volume, pressure and releasing process of helium bubble with its depth are acquired. The results show that with depth augmenting, the pressure of helium bubble increases gradually, while the volume decreases, but these two parameters are kept at some level when the depth is greater than 2.6 nm. Then, the evolutions of model system with helium bubble at various temperatures are simulated. The critical temperatures of helium bubble released from Ti surface at different depths are greatly different. On the whole, the critical temperature is in direct proportion to depth. But the releasing rates at different temperatures are almost unanimous. Finally, the mechanism of helium bubble released from Ti surface is explained on the basis of statistics and analyses of pressure of helium bubble and tensile strength of the metal thin film above the bubble. It is found that helium bubble would tear the Ti film above it when the pressure in helium bubble is greater than the strength of Ti film, and then helium atoms will be released from the metal.