温度对磨粒划擦单晶/多晶Al材料去除行为影响的分子动力学研究

Molecular dynamic study on effect of temperature on material removal behavior induced by grinding particle on scratching for single crystal/polycrystal Al

运用经典分子动力学方法对单晶/多晶Al材料去除行为与机制展开了研究。结果表明,受摩擦诱导作用,单晶Al塑性变形时更易产生螺型位错,螺型位错微观结构演化历经萌生、生长和繁衍3个阶段,且随温度升高,螺型位错萌生、生长和繁衍逐渐增多。多晶Al的晶界边缘是位错萌芽的发源地,更易产生新的位错。随着温度的增加,多晶Al的晶界范围逐渐扩张,晶粒框架发生改变,使得其晶界更易发生迁移。此外,摩擦中的单晶/多晶Al的水平切向力和法向力均随温度的升高呈线性下降,多晶Al的磨损性能弱于单晶Al,而多晶Al的摩擦因数高于单晶Al。单晶/多晶Al受摩擦诱导产生的磨屑原子数随滑动距离的增加而增加,且随温度升高呈类抛物线增长趋势。从纳观角度看,单晶/多晶Al材料去除形成磨屑的机制是材料的紧密接触区边缘应力集中导致的紧密接触区边缘的温度迅速上升,从而促进材料去除。

The material removal behavior and mechanism of single crystal/polycrystal Al were studied using classic molecular dynamics method.The results show that due to the friction induction effect,the screw dislocation is more likely to occur in single crystal Al during the plastic deformation,the screw dislocation microstructure evolution goes through three stages of initiation,growth and propagation,and with the increase of temperature,the initation,growth and propagation of screw dislocation gradually increase.The edge of polycrystal Al grain boundary is the origin of dislocation germination and is easy to generate new dislocation.With the increase of temperature,the grain boundary range of polycrystal Al gradually expands,the grain framework changes,which makes the grain boundary migrate easier.In addition,the horizontal tangential force and normal force of single crystal/polycrystal Al decrease linearly with the increase of temperature.The wear property of polycrystal Al is weaker than that of single crystal Al,while the friction factor of polycrystal Al is higher than that of single crystal Al.The atomic number of single crystal/polycrystal Al induced by friction increases with the increase of sliding distance,and it shows a parabolic increase trend with the increase of temperature.From the perspective of nanoscale,the friction chips formation mechanism due to material removal of single crystal/polycrystal Al is that the stress concentration at the edge of the close contact area of the material leads to the rapid rise of the temperature at the edge of the close contact area,which promotes the material removal.