Anormalous deformation behavior by first order and second order pyramidal slips in hcp metals.

对Cd、Zn、Mg单晶进行了[0001]拉伸试验。在[0001]拉伸实验中，Cd和Zn单晶的{1122}二级锥体滑移被激活。<1123>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。这些值低于[1120]拉伸的情况。Mg在[1120]拉伸中激活了二级锥体滑移。而在[0001]拉伸时，Mg单晶以{1012}孪晶屈服。为了研究合金元素对锥体滑移的影响，在77~293 K范围内对Mg-3.5、7.5、8.6、10.6和13.8at%Li合金单晶进行了[1120]拉伸实验。随着Li含量的增加，锥体滑移带中的剪切应变增大。认为Li的加入提高了（c + a）刃位错在二级锥滑移中的迁移率。在钛单晶中，棱镜 ...更多信息 在77~293K温度范围内，[1120]拉伸产生位错滑移;[0001]拉伸时，氧含量低（1300at.ppm）的Ti晶体产生{1012}孪晶，而氧含量高（4300at.ppm）的Ti晶体产生{1011}一级锥体滑移。<1123>在Lennard-Jones（L-J）势的分子动力学模拟中，（c + a）刃型位错在室温下具有理想的型芯结构，这种型芯在应变作用下转变为两个部分位错，并沿二级椭圆滑移面运动。在较高的温度下，核心扩展到基面，成为固着位错。在EAM势的情况下，Mg和Be在L-J势中表现出相同的结果。Ti的边缘核在{1122}面上具有窄核，在滑移面上不移动。（c + a）螺型位错的核心在室温下沿两个{1011}面扩展，在高温下向{1122}面扩展。螺杆芯在{1122}和{1011}之间通过双交叉滑动移动。这些结果在两种电位中都得到了。模拟结果表明，二次位错滑移的变形过程为：（c + a）刃型位错随温度升高而形成固着核结构，（c + a）螺型位错发生双错滑移，滑移带扩展。少

Cd, Zn and Mg single crystals were tested by [0001] tensile. {1122}<1123> second order pyramidal slip were activated in Cd and Zn single crystals by [0001] tensile test. Yields stress of each crystals increases with increasing temperature, namely anormalous temperature dependece. These values were lower than the case of [1120] tensile. In the case of Mg, second order pyramidal slip was activated in [1120] tensile. However, in the case of [0001] tensile, Mg single crystal were yield by {1012} twin. To investigate the effects of alloy element for pyramidal slip, Mg-3.5, 7,5, 8.6, 10.6 and 13.8at%Li alloy single crystals were tested by [1120] tensile in a range from 77K to 293K.Yield stress of second order pyramidal slip were decreased with increasing Li addition. Shear strains in slip bands of the pyramidal slip were increase with Li contents.. It is consider that mobility of (c+a) edge dislocation in second order pyramidal slip becomes high by Li addition. In Ti single crystals, prismat … More ic slip were occured by [1120] tensile in the range from 77K to 293K.In the case of [0001] tensile, Ti crystals which have low oxygen contents (1300at.ppm) yields by{1012} twin, however, Ti crystals with 4300at.ppm oxygen contents yield by {1011}<1123> first order pyramidal slip. Therefore, The pyramidal slip in Tiwill be active at higher oxygen contents.In molecular dynamics simulation using Lennard-Jones (L-J) potential, (c+a) edge dislocation have perfect type core structure at OK.This core changed into two partial dislocations by applying strain and moved on second order pyraidal slip plane. At higher temperature, the core extended to basal plane and became sessile dislocation. In the case of EAM potentials, Mg and Be shows same results in L-J potential. The edge core of Ti have narrow core on {1122} and did not move on the slip plane. Core of (c+a) screw dislocation extended on two {1011} plane at OK.The core extended to {1122} plnae at higher temperature. The screw core were moved between {1122} and {1011} by double cross slip. These resutls were obtained in both potentals. From simulation resuls, deformation process by secondary pyramial slip will summarized as follows : (c+a) edge dislocation becomes sessile core structure with increaseing tempreture, then double cross slip of (c+a) screw dislocation occures to propagete slip bands. Less