Mechanical Characterization of grain boundary strengthening through TEM in-situ indentation

对Fe-Si双晶进行了TEM原位压缩实验，发现位错通过晶界，没有堆积现象。结果表明，位错反应发生在晶界处。在变形过程中观察到螺杆和边缘两种类型的位错。透射电镜观察得到的载荷-位移曲线表明，以螺杆型为主，流动性越低，流变应力越大。另一数据显示了明显的屈服现象，随后出现了显著的应变软化。在这种情况下，位错密度随屈服后应变的增大而增大。因为在约翰斯顿-吉尔曼模型中，流动应力和位错密度之间的定量关系是可以理解的

TEM in-situ compression test was performed for Fe-Si bicrystal and revealed that dislocations passed through grain boundary without any pile-up. These results suggest that dislocation reaction occurs at grain boundary. We observed two types of dislocations of screw and edge during deformation. Load-displacement curves obtained with TEM observation shows that screw type dominant with lower mobility corresponds to higher flow stress. Another data shows obvious yield phenomenon and subsequently remarkable strain softening. In that case, dislocation density increases with strain after yielding. For the quantitative relationship between the flow stress and dislocation density is understood in the Johnston Gilman model