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

hcp 金属中一阶和二阶金字塔滑移的异常变形行为。

基本信息

批准号：
10650654
负责人：
TONDA Hideki
金额：
$ 2.24万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650654/
关键词：
dislocation pyramidal slip yield stress hcp metal core structre molecular dynamics computer simulation anormalous temperature dependence 錘面すべり hcp金属非底面すべり単結晶分子動学力学異状温度依存性

项目摘要

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

用[0001]拉伸法对Cd、Zn和Mg单晶进行了测试。[0001]拉伸试验表明，Cd和Zn单晶中{1122}<1123>的二阶锥体滑移被激活。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。这些数值低于[1120]拉伸的情况。在Mg的情况下，二级锥体滑移在[1120]拉伸中被激活。而在[0001]拉伸条件下，Mg单晶由{1012}孪晶生成。为了研究合金元素对锥体滑移的影响，在77K ~ 293K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]拉伸试验。二级锥体滑移屈服应力随Li添加量的增加而减小。锥体滑移带剪切应变随Li含量的增加而增加。认为Li的加入使（c+a）位错在二阶锥体滑移中的迁移率提高。在Ti单晶中，在77K ~ 293K范围内[1120]拉伸时，棱柱状晶的ic滑移较多。在[0001]拉伸的情况下，低氧含量（1300at.ppm）的Ti晶体产生{1012}孪晶，而含有4300at的Ti晶体产生{1012}孪晶。PPM含氧量产率{1011}<1123>一级锥体滑移。因此，在较高的氧含量下，tii的锥体滑移具有活性。利用Lennard-Jones （L-J）势进行分子动力学模拟，发现（c+a）边位错在OK处具有完美型核结构。该岩心在应变作用下变成两个局部位错，并在二阶锥体滑移面上移动。在较高温度下，芯向基面延伸，形成无柄位错。在EAM电位的情况下，Mg和Be在L-J电位中表现出相同的结果。Ti的边缘核在{1122}上有窄核，在滑移面上没有移动。（c+a）螺位错的核在两个{1011}平面上扩展。在较高的温度下，核心延伸到{1122}平面。螺杆芯在{1122}和{1011}之间通过双交叉滑块移动。这些结果是在两种电位下得到的。从模拟结果可以看出，二次锥体滑移的变形过程可以总结为：随着温度的升高，（c+a）边位错变成无底的核心结构，然后发生（c+a）螺位错的双交叉滑移，传播滑移带。少