单晶钽裂纹尖端的位错原位观察

马 莹,卢 艳,孔德利,舒新愉,邓青松,周 浩,王立华*,张 泽,韩晓东*

                                                单晶钽裂纹尖端的位错原位观察

马 莹1,卢 艳1,孔德利1,舒新愉1,邓青松1,周 浩1,王立华1*,张 泽2,韩晓东1*

  ( 1. 北京工业大学固体微结构与性能研究所,北京 100124;2.浙江大学电子显微镜中心,材料科学与工程学院,浙江 杭州310027)

摘  要  本文利用原创双金属片技术,在透射电子显微镜中实现了对小尺寸单晶钽(Ta)拉伸变形的原位实验观察。由于裂纹尖端的塑性区具有与材料整体塑性变形类似的特征,因此本实验针对裂纹尖端处的位错行为进行了研究。实验发现随着裂纹的扩展,有大量呈弯曲或钩状的位错不断形核,并朝着位错弯曲的部分滑移。在进一步的拉伸应力作用下,位错的长直部分不断长大并使这些位错在裂纹尖端堆积。对裂纹尖端的原位高分辨图像观察,发现在单晶钽中有大量伯氏矢量 b = 1/2<111> II型位错的形核和逃逸现象。 因此,证明这些混合位错对BCC单晶钽的塑性变形有一定贡献,并首次给出了纳米尺度材料中位错堆积的实验证据。

关键词 体心立方;单晶钽;裂纹尖端;混合型位错

中图分类号: TB383; O711+4; O77+2; TG115. 21+5. 3; TG115. 5+文献标识码:A   doi:10.3969/j.issn.1000-6281.2017.04.002

 

In situobservation of dislocations at crack tip in single crystalline tantalum

MA Ying1,LU Yan1,KONG De-li1,SHU Xin-yu1,DENG Qing-song1,ZHOU Hao1,WANG Li-hua1*,ZHANG Ze2,HAN Xiao-dong1*

( 1.Beijing Key Lab of Microstructure and Property of Advanced Materials,Beijing University of Technology,Beijing 100124;2.  Center of Electron Microscope,Zhejiang University,Hangzhou Zhejiang 310027,China)

 

Abstract   A new developed in situ TEM technology loaded by bimetallic strips is carried out to investigate the dislocation migration of single crystal tantalum (Ta) during tensile deformation. Typical dislocation behavior at crack tip is characterized carefully, which gives an actual procedure of nucleating and slipping of the curved and hook-like shaped dislocations. It is found that the long straight parts of dislocations grow and pile up at crack tip with increasing of tensile strain. Moreover, a lot of mixed dislocations with burgers vector of are found to nucleate and escape at the crack tip. The mixed dislocations provide significant contributionb = 1/2<111>to plastic deformation of BCC single crystal Ta. The experimental evidence of dislocations piling up in nano-scale Ta is obtained directly for the first time.

Keywords   BCC;single crystal Ta;crack tip;mixed dislocation

 

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