钨表面形貌控制及其在循环热载荷作用下的热疲劳性能

Surface morphology controlled of tungsten and its thermal fatigue behavior under cyclic heat loading

摘要:

钨作为聚变装置中的壁材料在各种循环热载荷作用下的热疲劳行为是一个重要的问题，它的热疲劳行为可能会受到其表面形貌的影响。为了解决这个问题，采用电子回旋共振（ECR）等离子体系统在多晶钨表面进行形貌控制实验，然后采用电子束设备对抛光和具有一定形貌的样品开展循环热载荷实验。结果表明表面形貌对在循环载荷下发生的循环塑性变形造成的损伤特征影响很小，在300次循环热载荷下某些晶粒中形成了微裂纹及挤出片结构，它们在不同晶粒中按着某一特定的方向平行排列。此外，在不同条件下通过等离子体刻蚀在钨表面制备了不同的三棱锥状和均匀的纳米结构。本文中，我们对损伤区域的截面进行了分析并给出了在循环热载荷下这种结构形成过程的示意图。

Abstract:

Thermal fatigue behavior under various cyclic heat loading is an important concern for tungsten as armor material in fusion devices. It may be significantly affected by its surface morphology. To address this issue, surface morphology controlled experiments have been performed on polycrystalline tungsten using an ECR plasma system and cyclic heat loading tests have been conducted upon the polished and modified samples using an electron beam facility. The results indicate that the surface topography has little effect on the characteristics of damage caused by the cycle plastic deformation during the cyclic heat loading. The micro-cracks and extrusions are formed in some grains after suffered 300 cyclic heat loading, which are aligned in different directions for varying grains. In addition, the modified specimens have fabricated both different triangular pyramid and homogeneous nanostructures by dry etching with different conditions. In this work, the cross-sectional surface of damage regions were analyzed and a set of schematic diagram was presented to explain the mechanism for the formation of micro-cracks and extrusions under cyclic heat loading.