Atomic-scale intergranular crack-tip plasticity in tilt grain boundaries acting as an effective dislocation source
Atomic-scale intergranular crack-tip plasticity in tilt grain boundaries acting as an effective dislocation source
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DOI：
10.1016/j.actamat.2015.01.002
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发表时间：
2015-04
期刊：
影响因子：
9.4
通讯作者：
T. Shimokawa;Masaaki Tsuboi
中科院分区：
文献类型：
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作者：
T. Shimokawa;Masaaki Tsuboi
塑性变形结晶材料的沿晶断裂韧性受沿晶裂纹尖端前的塑性功的强烈控制。因此，在研究晶间断裂韧性时，应将晶界视为解理面和位错源。结合连续统分析和原子模拟，研究了<1 1 2>倾斜GBs作为有效位错源的晶间裂纹尖端塑性的原子尺度机制。为了定量预测晶间裂纹尖端附近的第一次塑性变形，我们首先模拟了在晶间裂纹尖端之前的GBs的位错发射，并分析得出了临界应力强度因子。如果预测的第一塑性现象是位错从GBs发射，那么由此产生的楔形偏斜可以屏蔽裂纹附近的应力场。裂纹尖端的位错发射伴随着GBs的位错发射，尽管后者预测困难。晶格缺陷的演化在裂纹尖端前的三结处形成具有斜纹的纳米晶粒，从而削弱了裂纹尖端附近的力学场。因此，在提高材料的晶间断裂韧性时，不可忽视GBs作为位错源的作用。
The intergranular fracture toughness of plastic deformable crystalline materials is strongly controlled by the plastic work ahead of the intergranular crack tip. Therefore, in studies of intergranular fracture toughness, the grain boundaries (GBs) should be regarded as both a cleavage plane and dislocation source. Combining continuum analyses and atomic simulations, this study investigates the atomic-scale mechanism of intergranular crack tip plasticity in aluminum <1 1 2> tilt GBs as an effective dislocation source. To quantitatively predict the first plastic deformation near the intergranular crack tip, we first model the dislocation emission from the GBs ahead of the intergranular crack tip and analytically derive the critical stress intensity factor. If the predicted first plastic phenomenon is dislocation emission from the GBs, the resulting wedge disclination can shield the stress field near the crack. Dislocation emissions from the crack tip are accompanied by dislocation emissions from the GBs, despite the predicted difficulty of the latter. The lattice defect evolution nucleates a nanograin with a disclination at the triple-junction ahead of the crack tip, which can weaken the mechanical field near the crack tip. Consequently, when improving the intergranular fracture toughness of materials, the role of GBs as dislocation sources cannot be ignored.