Meso-scale analysis for peculiar mechanisms of pyramidal slip in hcp metals

通过[112^^-0]在77K -293K范围内的拉伸试验，在Mg和Mg- li单晶中激活了{112^^-2}<<11>^^ -23>的二阶锥体滑移。各晶体的屈服应力随温度的升高而增大，即反常的温度依赖性。在293K -473k范围内锥体滑移也被激活，棱柱滑移不存在。锥体滑移活性与多晶镁的延展性有关。{101^^-1}<<11>^^ -23>一级锥体滑移在[0001]拉压作用下被激活。[112^^-0]和[11^^-00]拉伸和压缩条件下棱柱滑移的屈服应力不同，但施密德系数相同。在Lennard-Jones （L-J）势的分子动力学模拟中，（c+a）螺位错的核扩展在两个{101^^-1}平面上。螺芯通过双交叉滑移在{112^^-2}和{101^^-1}之间移动。（c+a）边位错有两种核结构。两种类型的岩心均不向负份额和[112^^-0]压缩方向移动。部分位错芯受[0001]拉伸和压缩作用，应力随加载方向变化不大。结果表明，（c+a）边位错的运动不仅受剪切应力的影响，还受滑移面上法向应力的影响。从模拟结果可以总结出二次锥体滑移的变形过程。

{112^^-2}<<11>^^^-23> second order pyramidal slip was activated in Mg and Mg-Li single crystals by [112^^-0] tensile test in the range of 77K -293K. Yields stress of each crystal increase with increasing temperature, namely anomalous temperature dependence. The pyramidal slip were also activated in the range of 293K -473k and there is no prismatic slip. Activities of pyramidal slip was related to ductility of polycrystalline magnesium.{101^^-1}<<11>^^^-23> first order pyramidal slip was activated in [0001] tensile and compression. Yield stress of prismatic slip in [112^^-0] and [11^^-00] tension and compression were different in spite of same Schmid's factor.In molecular dynamics simulation using Lennard-Jones (L-J) potential, the core of (c+a) screw dislocation extended on two {101^^-1} plane. The screw core was moved between {112^^-2} and {101^^-1} by double cross slip.(c+a) edge dislocation have two type of core structures. Both type of core are not move in negative share and [112^^-0] compression. Partial dislocation cores move by [0001] tensile and compression, and the stress is little different by loading direction. These results shows that motion of (c+a) edge dislocation is affected not only shear stress but also normal stress on slip plane.From simulation results can summarize the deformation process by secondary pyramidal slip.