Hydrogen-microstructure interactions in iron-based alloys at small scales: from amorphous, via nanocrystals, to polycrystals

氢脆（HE）是钢中最受关注的问题，它会导致材料失效，从而造成巨大的经济损失。过去的研究主要集中在钢中的HE，在非晶合金中的HE研究较少，而在纳米晶材料中的HE研究较少。尽管对晶体合金进行了多项研究，但仍然缺乏基本的理解，并且关于H的具体影响和导致材料失效的机制存在争议。本计画将提供不同原子序铁基合金在小长度尺度下氢对力学行为影响的知识。在电化学充电过程中的机械，化学和电化学性能的相互作用将通过原位纳米压痕研究H。样品将由Cr含量接近不锈钢的单相Fe合金组成：非晶Fe 50 Cr 15 Mo 15 C14 B6、纳米晶和多晶铁素体Fe-Cr合金。特别感兴趣的是不同的变形机制：剪切带在非晶合金和位错塑性结晶的，以及它们各自的响应由于H吸收。纳米晶合金将进行研究，以阐明剪切带和位错为主的制度在HE的相互作用。我们将确定开始的塑性，硬度和弹性模量的带电和不带电的样品作为脆化的指标。在晶体合金中的晶界处的机械测试将证明H效应和应力集中区域中可能的脱粘。微观结构变化的具体数据将通过高分辨率技术获得，如透射电子显微镜、原子力显微镜和电子沟道衬度成像。H浓度和渗透将通过热脱附光谱和扫描Kelvin探针测量来量化，以将机械和微观结构数据与结构中的H量和位置相关联。关于HE现象和H吸收对Fe合金的机械响应的影响的基本见解，从位错塑性转变为剪切带，将对材料长期稳定性的未来改进具有有价值的意义。

Hydrogen embrittlement (HE), which is of prime concern in steels, causes material failure and thus huge economic losses. In the past, several studies focused on HE in steels, much less in amorphous alloys, and few are found for nanocrystalline materials. Despite the multiple studies on crystalline alloys, there is still a lack of fundamental understanding and exists controversy regarding the specific effects of H and the mechanisms leading to failure of the material. This project will provide knowledge on the H effects on the mechanical behavior at small length scales in Fe-based alloys with different atomic ordering. The interplay of mechanical, chemical and electrochemical properties will be studied by in-situ nanoindentation during electrochemical charging of H. The samples will consist of single phase Fe alloys with Cr contents close to that of stainless steel: amorphous Fe50Cr15Mo15C14B6, nanocrystalline and polycrystalline ferritic Fe-Cr alloys. Of special interest are the distinct deformation mechanisms: shear bands in amorphous alloys and dislocation plasticity in crystalline ones, and their respective response due to H absorption. Nanocrystalline alloys will be studied to elucidate the interplay of shear band and dislocation dominated regimes during HE. We will identify the onset of plasticity, hardness and elastic modulus of charged and uncharged samples as indicators for embrittlement. Mechanical testing at grain boundaries in crystalline alloys will evidence the H effects and possible decohesion in regions of stress concentration. Specific data on the microstructural changes will be obtained by high resolution techniques, such as transmission electron microscopy, atomic force microscopy and electron channeling contrast imaging. H concentration and permeation will be quantified by thermal desorption spectroscopy and scanning Kelvin probe measurements to correlate the mechanical and microstructural data with the H amount and location within the structure.The fundamental insights on the HE phenomena and the effects of H absorption on the mechanical response of Fe alloys, shifting from dislocation plasticity to shear banding, will be of valuable interest for the future improvement of the materials long-term stability.