Twin Nucleation by Slip Transfer across Grain Boundaries in Commercial Purity Titanium
Twin Nucleation by Slip Transfer across Grain Boundaries in Commercial Purity Titanium
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DOI：
10.1007/s11661-009-0097-6
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发表时间：
2010-02
期刊：
影响因子：
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通讯作者：
Leyun Wang;Y. Yang;P. Eisenlohr;T. Bieler;M. Crimp;D. E. Mason
中科院分区：
文献类型：
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作者：
Leyun Wang;Y. Yang;P. Eisenlohr;T. Bieler;M. Crimp;D. E. Mason
应变传递在晶界变形孪生激活中的作用已在弯曲变形的商业纯钛中得到表征。织构多晶的两个不同取向在弯曲时变形，并使用电子背散射衍射（EBSD）进行分析，以确定表面拉伸区域中的主动滑移和孪生系统。棱柱滑移和孪生是两个方向上最广泛观察到的变形模式。非棱柱滑移系统也被激活，最有可能适应局部应变异质性。软/硬晶粒对的滑移刺激孪晶成核机制被确定：当滑移系统与孪晶系统良好对准时，软取向晶粒中的位错滑移可以刺激相邻硬晶粒中的孪晶成核。这种排列是通过滑移传递参数 m′ 来描述的。[24]在六个可用的孪生系统中，由这种机制激活的孪生总是具有最高的 m' 值，而基于全局（单轴拉伸）应力状态的施密德因子是孪生活动的不太重要的指标。尽管整体施密德因子非常低，但通过滑移传递，有时会形成变形孪晶。滑移刺激孪晶成核的频率很大程度上取决于材料的织构和加载方向。对于其中一个晶粒具有较大施密特孪晶因子的晶粒对，非参数统计分析证实，那些具有较大 Schmid 因子的晶粒更有可能表现出滑移刺激孪晶。
The role of strain transfer in the activation of deformation twinning at grain boundaries has been characterized in commercially pure titanium deformed in bending. Two different orientations of a textured polycrystal were deformed in bending and were analyzed using electron backscattered diffraction (EBSD) to determine the active slip and twinning systems in the surface tensile region. Prismatic slip andtwinning were the most widely observed deformation modes in both orientations. Nonprismatic slip systems were also activated, most likely to accommodate local strain heterogeneities. A slip-stimulated twin nucleation mechanism was identified for soft/hard grain pairs: dislocation slip in a soft-oriented grain can stimulate twin nucleation in the neighboring hard grain when the slip system is well aligned with the twinning system. This alignment was described by a slip-transfer parameterm′.[24] Twins activated by this mechanism always had the highestm′ value among the six availabletwinning systems, while the Schmid factor, based on the global (uniaxial tensile) stress state, was a less significant indicator of twin activity. Through slip transfer, deformation twins sometimes formed despite having a very low global Schmid factor. The frequency of slip-stimulated twin nucleation depends strongly on the texture and loading direction in the material. For grain pairs having one grain with a large Schmid factor for twinning, nonparametric statistical analysis confirms that those with a largerm′ are more likely to display slip-stimulated twinning.