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

{112在<11>77 K ~ 293 K范围内，通过[112^^-0]拉伸实验，发现Mg和Mg-Li单晶中存在着&lt; ^^-2}&lt; ^^-23&gt;二级锥体滑移。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293 K-473 K温度范围内，锥体滑移也被激活，但没有棱柱滑移。多晶镁的塑性与锥体滑移活动有关。{101在<11>[0001]拉伸和压缩过程中，激活了^^-1}&lt; ^-23&gt;一级锥体滑移。尽管Schmid因子相同，但[112^^-0]和[11^^-00]拉伸和压缩条件下滑移滑移的屈服应力不同，在Lennard-Jones（L-J）势的分子动力学模拟中，（c+a）螺型位错核心在两个{101^^-1}面上延伸。螺杆芯通过双交叉滑动在{112^^-2}和{101^^-1}之间移动。（c+a）刃型位错有两种核心结构。这两种类型的核心都不是在负份额和[112^^-0]压缩中移动。部分位错核以[0001]拉压方式运动，应力随加载方向变化不大。结果表明，（c+a）刃型位错的运动不仅受到滑移面上剪应力的影响，而且受到滑移面上正应力的影响，模拟结果可以概括二次锥滑移的变形过程。

{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.