Ii Seiichiro, Enami Takero, Ohmura Takahito, Tsurekawa Sadahiro
Research Center for Structural Materials, National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
Department of Materials Science and Engineering, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan.
Materials (Basel). 2021 Mar 15;14(6):1431. doi: 10.3390/ma14061431.
Transmission electron microscopy in situ straining experiments of Al single crystals with different initial lattice defect densities have been performed. The as-focused ion beam (FIB)-processed pillar sample contained a high density of prismatic dislocation loops with the <111> Burgers vector, while the post-annealed specimen had an almost defect-free microstructure. In both specimens, plastic deformation occurred with repetitive stress drops (∆). The stress drops were accompanied by certain dislocation motions, suggesting the dislocation avalanche phenomenon. ∆ for the as-FIB Al pillar sample was smaller than that for the post-annealed Al sample. This can be considered to be because of the interaction of gliding dislocations with immobile prismatic dislocation loops introduced by the FIB. The reloading process after stress reduction was dominated by elastic behavior because the slope of the load-displacement curve for reloading was close to the Young's modulus of Al. Microplasticity was observed during the load-recovery process, suggesting that microyielding and a dislocation avalanche repeatedly occurred, leading to intermittent plasticity as an elementary step of macroplastic deformation.
对具有不同初始晶格缺陷密度的铝单晶进行了透射电子显微镜原位应变实验。聚焦离子束（FIB）处理后的柱状样品含有高密度的具有<111>柏氏矢量的棱柱位错环，而退火后的样品具有几乎无缺陷的微观结构。在两个样品中，塑性变形都伴随着重复的应力下降（∆）。应力下降伴随着某些位错运动，表明存在位错雪崩现象。FIB处理后的铝柱状样品的∆小于退火后铝样品的∆。这可以认为是由于滑移位错与FIB引入的固定棱柱位错环相互作用的结果。应力降低后的再加载过程以弹性行为为主，因为再加载的载荷-位移曲线斜率接近铝的杨氏模量。在载荷恢复过程中观察到了微塑性，表明微屈服和位错雪崩反复发生，导致间歇性塑性作为宏观塑性变形的基本步骤。
