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+2 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
全文下载请到同方知网、万方数据库或重庆维普等数据库中下载!
[1] CHRISTIAN J W. Some surprising features of the plastic deformation of body-centered cubic metals and alloys [J]. Metallurgical and Materials Transactions A, 1983, 14(7): 1237-1256.
[2] SEEGER A. Peierls barriers, kinks, and flow stress: recent progress [J]. Zeitschrift für Metallkunde,2002,93(8):760-777.
[3] VITEK V, PAIDAR V. Non-planar dislocation cores: a ubiquitous phenomenon affecting mechanical properties of crystalline materials [J]. Dislocations in Solids,2008,14(07):439-514.
[4] WEINBERGER C R, CAI W. Surface-controlled dislocation multiplication in metal micropillars [J]. Proceedings of the National Academy of Sciences, 2008, 105(38): 14304-14307.
[5] HUANG L, LI Q J, SHAN Z W, et al. A new regime for mechanical annealing and strong sample-size strengthening in body centred cubic molybdenum [J]. Nature Communications,2011,2(1):547.
[6] GREER J R, WEINBERGER C R, CAI W. Comparing the strength of fcc and bcc sub-micrometer pillars: compression experiments and dislocation dynamics simulations [J]. Materials Science and Engineering: A, 2008, 493(1): 21-25.
[7] BRINCKMANN S, KIM J Y, GREER J R. Fundamental differences in mechanical behavior between two types of crystals at the nanoscale [J]. Physical Review Letters, 2008, 100(15): 155502.
[8] BULATOV V V, HSIUNG L L, TANG M, et al. Dislocation multi-junctions and strain hardening [J]. Nature, 2006, 440(7088): 1174-1178.
[9] MIN HAN S, FENG G, YOUNG JUNG J, et al. Critical-temperature/Peierls-stress dependent size effects in body centered cubic nanopillars [J]. Applied Physics Letters, 2013, 102(4): 041910.
[10]ALLEMAN C, GHOSH S, LUSCHER D J, et al. Evaluating the effects of loading parameters on single-crystal slip in tantalum using molecular mechanics [J]. Philosophical Magazine, 2014, 94(1): 92-116.
[11]HALE L M, ZIMMERMAN J A, WEINBERGER C R. Simulations of bcc tantalum screw dislocations: why classical inter-atomic potentials predict {112} slip [J]. Computational Materials Science, 2014, 90: 106-115.
[12]ITO K, VITEK V. Atomistic study of non-Schmid effects in the plastic yielding of bcc metals [J]. Philosophical Magazine A, 2001, 81(5): 1387-1407.
[13]GRÖGER R, BAILEY A G, VITEK V. Multiscale modeling of plastic deformation of molybdenum and tungsten: I. atomistic studies of the core structure and glide of 1/2< 111> screw dislocations at 0K [J]. Acta Materialia, 2008, 56(19): 5401-5411.
[14]WANG L, HAN X, LIU P, et al. In situ observation of dislocation behavior in nanometer grains [J]. Physical Review Letters, 2010, 105(13): 135501.
[15]WANG L, ZHANG Z, MA E, et al. Transmission electron microscopy observations of dislocation annihilation and storage in nanograins [J]. Applied Physics Letters, 2011, 98(5): 051905.
[16]WANG L, TENG J, LIU P, et al. Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum [J]. Nature Communications, 2014, 5(5):4402.
[17]GRÖGER R, VITEK V. Explanation of the discrepancy between the measured and atomistically calculated yield stresses in body-centred cubic metals [J]. Philosophical Magazine Letters, 2007, 87(2): 113-120.
[18]SCHNEIDER A S, KAUFMANN D, CLARK B G, et al. Correlation between critical temperature and strength of small-scale bcc pillars [J]. Physical Review Letters, 2009, 103(10): 105501.
[19] KAUFMANN D, MÖNIG R, VOLKERT C A, et al. Size dependent mechanical behaviour of tantalum [J]. International Journal of Plasticity, 2011, 27(3): 470-478.