Stress fields and geometrically necessary dislocation density distributions near the head of a blocked slip band
Stress fields and geometrically necessary dislocation density distributions near the head of a blocked slip band
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DOI：
10.1016/j.actamat.2012.07.004
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发表时间：
2012-09-01
期刊：
影响因子：
9.4
通讯作者：
Wilkinson, Angus J.
中科院分区：
文献类型：
--
作者：
Britton, T. Benjamin;Wilkinson, Angus J.
我们已经研究了一个阻塞滑移带和变形钛晶界的相互作用，使用高分辨率电子背散射衍射和原子力显微镜。从这些观察，我们推断出活跃的位错类型，并评估了所选晶粒内的位错反应。位错源已被激活的棱镜滑移面，产生一个平面滑移带和堆积的位错在近螺旋排列在晶界。这种堆积导致邻近晶粒中塑性的激活，并在堆积中留下具有许多位错的边界。检查的弹性应力状态之前的堆积揭示了一个特征的“一个超过距离的平方根”的依赖性的剪切应力上解决的活动滑移面。这一观察结果验证了Eshelby，Frank和Nabarro在1951年给出的位错力学模型，尽管它在支持我们对晶粒尺寸强化，断裂萌生，短疲劳裂纹扩展，疲劳裂纹萌生和许多其他现象的理解方面很重要，但以前没有直接测试过。该分析还提供了一种方法来测量多晶材料中单个晶界的滑移转移阻力。对于边界和滑移系统分析这里的Hall-Petch系数K = 0.41 MPa m（1/2）被确定。(C)2012 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
We have examined the interaction of a blocked slip band and a grain boundary in deformed titanium using high-resolution electron backscatter diffraction and atomic force microscopy. From these observations, we have deduced the active dislocation types and assessed the dislocation reactions involved within a selected grain. Dislocation sources have been activated on a prism slip plane, producing a planar slip band and a pile-up of dislocations in a near screw alignment at the grain boundary. This pile-up has resulted in activation of plasticity in the neighbouring grain and left the boundary with a number of dislocations in a pile-up. Examination of the elastic stress state ahead of the pile-up reveals a characteristic "one over the square root of distance" dependence for the shear stress resolved on the active slip plane. This observation validates a dislocation mechanics model given by Eshelby, Frank and Nabarro in 1951 and not previously directly tested, despite its importance in underpinning our understanding of grain size strengthening, fracture initiation, short fatigue crack propagation, fatigue crack initiation and many more phenomena. The analysis also provides a method to measure the resistance to slip transfer of an individual grain boundary in a polycrystalline material. For the boundary and slip systems analysed here a Hall-Petch coefficient of K = 0.41 MPa m(1/2) was determined. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.