材料科学
晶界
软化
晶体孪晶
成核
纳米压痕
位错
聚结(物理)
晶界强化
硬化(计算)
复合材料
钨
粒度
冶金
微观结构
热力学
物理
图层(电子)
天体生物学
作者
William H. Cunningham,Yang Zhang,Spencer L. Thomas,Osman El-Atwani,Yongqiang Wang,Jason R. Trelewicz
出处
期刊:Acta Materialia
[Elsevier]
日期:2023-06-01
卷期号:252: 118948-118948
被引量:3
标识
DOI:10.1016/j.actamat.2023.118948
摘要
The formation of helium cavities in coarse-grained materials produces hardening proportional to the number density and size of the cavities and due to the interaction of dislocations with intragranular helium defects. In nanostructured metals containing a high density of interfacial sinks, preferential cavity formation in the grain boundaries instead produces softening that is often attributed to enhanced interfacial plasticity. Employing two grades of ultrafine-grained tungsten, we explore this effect using targeted implantation studies to map cavity evolution as a function of the irradiation conditions and quantify its impact on the mechanical response through nanoindentation. Softening is reported at implantation temperatures above the threshold for preferential grain boundary cavity formation but at a sufficiently low fluence prior to the growth of intragranular cavities. Collective changes in the mean cavity size, density, and morphology beneath a residual impression on an implanted surface indicate that cavity coalescence accompanied the reduction in hardness. Complementary atomistic simulations demonstrate that, in tungsten grain structures exhibiting softening, grain boundary bubble coalescence is driven by stress concentrations that further act to localize strain in the grain boundaries through cooperative deformation processes involving local atomic shuffling and sliding, dislocation emission, and even the nucleation of unstable twinning events.
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