Orientation-dependent indentation response of helium-implanted tungsten
Orientation-dependent indentation response of helium-implanted tungsten
复制标题
DOI：
10.1063/1.5097403
复制
发表时间：
2019-03
影响因子：
4
通讯作者：
Suchandrima Das;Hongbing Yu;E. Tarleton;F. Hofmann
中科院分区：
文献类型：
--
作者：
Suchandrima Das;Hongbing Yu;E. Tarleton;F. Hofmann
对离子注入材料中纳米压痕形貌研究的文献综述揭示了似乎不一致的观察结果，有堆积和下沉的报道。这可能是由于被测样品点的晶体取向，在评估植入引起的变形响应变化时通常不考虑这一点。本文研究了纯钨和氦注入钨中球形纳米压痕的取向依赖性，考虑了面外取向和面外取向晶粒。原子力显微镜（AFM）显示，未植入钨的压痕与取向无关。然而，在植入材料中，颗粒的堆积比取向的堆积更大，更局部。根据对晶粒的观察，我们假设由于氦诱导缺陷引起的大的初始硬化随后是局部缺陷去除和随后的应变软化。基于这一假设建立的压痕过程的晶体塑性有限元模型，准确地再现了实验观察到的压痕形貌的取向依赖性。结果表明，控制氦诱导缺陷与滑移位错相互作用的机制与取向无关。相反，堆积形态的差异是由于晶体滑移系统、样品表面和球形压头的相对取向。这突出了在使用纳米压痕探测离子注入材料的变形行为时，考虑晶体取向的重要性。
A literature review of studies investigating the topography of nano-indents in ion-implanted materials reveals seemingly inconsistent observations, with report of both pile-up and sink-in. This may be due to the crystallographic orientation of the measured sample point, which is often not considered when evaluating implantation-induced changes in the deformation response. Here we explore the orientation dependence of spherical nano-indentation in pure and helium-implanted tungsten, considering grains with , and out-of-plane orientations. Atomic force microscopy (AFM) of indents in unimplanted tungsten shows little orientation dependence. However, in the implanted material a much larger, more localised pile-up is observed for grains than for and orientations. Based on the observations for grains, we hypothesise that a large initial hardening due to helium-induced defects is followed by localised defect removal and subsequent strain softening. A crystal plasticity finite element model of the indentation process, formulated based on this hypothesis, accurately reproduces the experimentally-observed orientation-dependence of indent morphology. The results suggest that the mechanism governing the interaction of helium-induced defects with glide dislocations is orientation independent. Rather, differences in pile-up morphology are due to the relative orientations of the crystal slip systems, sample surface and spherical indenter. This highlights the importance of accounting for crystallographic orientation when probing the deformation behaviour of ion-implanted materials using nano-indentation.