First Direct In Situ Observation of Grain Boundary Sliding in Ultrafine Grained Noble Metal
First Direct In Situ Observation of Grain Boundary Sliding in Ultrafine Grained Noble Metal
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DOI：
10.1002/adem.201300413
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发表时间：
2014-05
影响因子：
3.6
通讯作者：
Kejing Yang;H. Fecht;Y. Ivanisenko
中科院分区：
文献类型：
--
作者：
Kejing Yang;H. Fecht;Y. Ivanisenko
O DOI：10.1002/adem.201300413 M M U N IC First Direct In Situ Observation of Grain Boundary Sliding in Ultrafine Grained贵金属中晶界滑动的首次直接原位观察 ** A T I由Kejing Yang，Hans-J€ org Fecht和Yulia Ivanisenko* O N塑性本质的基本问题最近，Kurmanaeva等人发现，具有非常小晶粒尺寸的材料的大体积样品吸引了科学和技术的极大关注。理论估计预测，当晶粒尺寸减小到几纳米时，位错的成核和增殖--常规结晶固体中塑性变形的主要过程，以及塑性剪切穿过晶界的传播需要不切实际的高应力。在这种制度下，基于极大地增加面积的晶界分子动力学（MD）模拟建议替代和潜在的新的变形机制，如晶界滑动（GBS）结合晶粒旋转，以适应几何约束。然而，到目前为止，由于分析技术的技术障碍，在如此小的晶粒尺寸下，几乎没有发现晶粒边界介导的变形过程的直接证据。例如，Shan等人使用原位透射电子显微镜（TEM）技术报道了晶粒旋转。研究了超细晶纯铝（UFG）抛光表面和UFGAl-6082合金拉伸后产生的深度感应压痕周围GBS的室温形变后的形变缓减特性。由于TEM样品的高表面积与体积比，报告可能会受到人为因素的影响，参考文献中的结论。并没有通过晶粒的取向成像来证实，以表明所出现的表面裂纹确实是沿着沿着发生的。此外，临界实验需要提供物理证据来证明或反驳理论基础上预测的介观变形机制，以澄清争议和猜测。
O DOI: 10.1002/adem.201300413 M M U N IC First Direct In Situ Observation of Grain Boundary Sliding in Ultrafine Grained Noble Metal** A T I By Kejing Yang, Hans-J€ org Fecht and Yulia Ivanisenko* O N The fundamental problem of the nature of plasticity in Recently, Kurmanaeva et al. found that bulk samples of materials with very small grain size attracts a great attention for science and technology. Theoretical estimates predict that nucleation andmultiplication of dislocations – the primary careers of plastic deformation in conventional crystalline solids, and propagation of plastic shear across grain boundaries require unrealistically high stresses when the grain size decreases to a few nanometers. In this regime, based on the immensely increased area of grain boundaries molecular dynamic (MD) simulations suggest alternative and potentially new deformation mechanisms, such as grain boundary sliding (GBS) combined with grain rotations in order to accommodate geometric constraints. However, so far little direct evidence on grain boundary-mediated deformation processes at such small grain sizes has been found due to technical barriers of analytical techniques. For example, Shan et al. reported grain rotation using in situ transmission electron microscope (TEM) techniques. Deformation relief characteristic of GBS was observed after room temperature deformation around depth-sensing indentations produced on the polished surfaces of pure aluminumultrafine-grained (UFG) samples and also in an UFGAl-6082 alloy after tensile testing. While report may suffer from artifacts due to the high surface-to-volume ratio of the TEM sample, conclusions in refs. were not verified by orientation imaging of grains to show that appeared surface cracks indeed occurred along grain boundaries. Further, critical experiments are required to provide physical evidence to prove or disprove the mesoscopic deformation mechanisms predicted on a theoretical basis in order to clarify the controversy and speculation.