The grainboundary might absorb dislocations emitted from the crack tip , and emitted dislocations into neighbor grain , and them leaving behind a dislocation free zone in the front of a grainboundary , this kind of dislocation free zone 首次发现黄铜裂尖前方形变孪晶，微裂纹在各个孪晶中形核、扩展，然后相互连接，使裂纹呈z字形扩展。
In this investigation , three types of twins were observed in the deformation microstructures of ct20 alloy at cryogenic temperature . that is , twins of { 11 2 ~ l } , { 10 t2 } and { li 22 } type . while only { 11 2 ~ 2 } type twin was found in ct20a alloy 在本文研究的ct20合金低温下变形的组织中观察到了三种类型的孪晶，即{一l丁l } 、 { 20了2 }和{一l玄2 }型孪晶; etzoa合金中目前只观察到了{ 11丁2 }型孪晶。
Quite notable { 11 22 } twins with the appearance of strip piercing through lamellar colony were found in the tensile microstructure of ct20a alloy by tem analyzing , while no deformation twinning was found in the microstructure of alloy with high oeq Ct20a合金低氧当量拉伸试样的tem组织中有相当数量的{ 11几}型孪晶存在，孪晶在形貌上表现为穿过几个片的细条。高氧当量试样中没有观察到变形孪晶的存在。
When ct20 alloy was tensioned at 20k , the main deformation mechanism in equiaxed microstructure was the slip of dislocations , and in bimodal microstructure the slip of dislocations and a small amount of twinning and in lamellar microstructure a large amount of twinning Ct20合金20k拉伸变形时，等轴组织主要是位错的滑移起主导作用，双态组织除了位错滑移外还有少量的变形孪晶产生，片状组织中则能观察到数量较多的孪晶。
It can be noticed that both r and t specimens show initial hardening and subsequent softening at the strain amplitude higher than 0 . 8 % and cyclic softening from the beginning to fracture under strain amplitude less than 0 . 8 % at room temperature , and the cyclic flow stress was always lower in r specimen than in t specimen at the same strain range 且在相同的应变幅下， t向试样比r向试样具有更高的循环流变应力。此外，对r向及t向试样，低应变幅下呈现出循环软化现象是因为晶粒旋转导致循环软化；而在高应变幅下发生循环硬化是由于孪晶作用的结果。
Recently bulk tb - dy - fe single crystals have been obtained by magnetic levitation cold crucible without contamination in wuhan university of technology . these excellent single crystals , possessing a large displacement output under low magnetic field , build a foundation for the fabrication of the high precision micro - displacement actuators . the purpose of this research is to manufacture an advanced micro - displacement actuator with this high performance single crystal as the driving unit 常规的磁致伸缩型微位移致动器大多采用多晶或具有孪晶结构的磁致伸缩材料作为驱动单元，由于晶界和孪晶界对畴壁的移动具有阻碍作用，其低场下的位移输出较小，调控精度受到很大影响。
The macroscopic defects such as twins , small - cracking , scattering particles , growth layer and cores are examined ; they are related with the temperature difference between gas and melt : the twins and small - cracking come out when the difference is large , the bubbles and scattering particles come out when that is small 观察到了孪晶、裂隙、云层、生长层和核心等宏观缺陷，晶体的这些宏观缺陷与气- -液界面温差有较大关系：温差大容易造成孪晶、裂隙等缺陷；温差小容易造成气泡、散射颗粒等缺陷。
