晶界内耗研究的进展

Progress in the Investigations of Grain Boundary Internal Friction

固体在机械振动过程中由于材料内部原因引起的能量损耗称为内耗。晶界内耗峰是我国科学家葛庭燧于1947年用他发明的"葛氏扭摆"在多晶纯铝中发现的。晶界内耗峰和相关的滞弹性效应可以用滞弹性理论和粘滞性滑动模型给予合理的解释。这个内耗峰已被广泛地用来研究晶界的动力学行为,杂质在晶界的偏聚,以及材料科学中相关的问题。以往晶界内耗的研究大多数是用多晶试样进行的,其中包含了不同类型晶界的贡献。由于不同类型晶界的结构和性质不同,因而多晶试样中的晶界内耗只能反映不同晶界的"平均效应",它的具体机制也难以解释清楚。二十一世纪以来,人们对双晶试样(其中只包含单一晶界)中的晶界内耗进行了比较细致的研究。实验结果表明,晶界内耗可以反映不同类型晶界的"个性",因而可以应用于"晶界的设计和控制"(或称"晶界工程")。此外,新近还发现了晶界内耗中的"耦合效应"和"补偿效应"。这些发现加深了对晶界内耗机制的认识。本文首先对以往多晶试样中的晶界内耗研究做一个简要的概述,然后介绍近年来双晶试样中晶界内耗研究的新进展,并对晶界内耗的微观机制和应用前景进行分析和展望。

Internal friction （or damping） is a measure of energy dissipation during mechanical vibration. The internal friction peak induced by grain boundary （GB） relaxation was discovered by Ke in polycrystals in 1947 by using his invented ＂Ke pendulum＂. The GB internal friction and related anelastic effects can be successfully interpreted in terms of Zener＇s anelastic theory and viscous sliding model. Since then, the GB internal friction peak has been widely used to study the dynamic process of GBs, impurity segregation at GBs and relevant processes in materials science. Previously, the GB internal friction was mostly studied with polycrystalline materials, in which mixed contributions of different types of GBs are involved. Since the microstructures and behaviors of different types of GBs are different, such internal friction can only reveal the general behaviors of GBs, while the detailed mechanism of the GB peak in polycryatals is hardly clarified. From the beginning of the 21th century, the internal friction in bicrystals （each has a single boundary） has been systematically investigated. The results indicate that the internal friction can be used to distinguish the individual behavior of different types of GBs and applied to the practice of ＂GB design and control＂ （or ＂GB engineering＂）. Moreover, the coupling effect and compensation effect involved in GB relaxation has been recently revealed and explained. These findings improve the understanding of the mechanism of GB internal friction. The present paper attempts to give a comprehensive review to the investigations of GB internal friction＇ in polycrystals, bamboo-crystals and bicrystals. The microscopic mechanisms and the further applications of GB internal friction are discussed and prospected.