Advanced experiments for characterizing and understanding hydrogen-assisted mechanical degradation

用于表征和理解氢辅助机械降解的高级实验

• 批准号: 373150815
• 负责人: Professor Dr. Christian Motz, since 3/2019
• 金额: --
• 依托单位: Ecole Nationale Supérieure des Mines de Saint-Étienne
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/373150815?language=en
• 关键词: Advanced; experiments; characterizing; understanding; hydrogen

Presence of hydrogen in metals causes often a change in fracture mode from ductile transgranular to less ductile or brittle intergranular. For understanding the role and mechanisms of hydrogen induced degradation, it is necessary to know the local hydrogen concentration inside the grains and more especially at material inhomogeneities like grain boundaries (GBs). During this project, AFM-based scanning Kelvin probe force microscopy (SKPFM) will be used for studying local hydrogen distribution at coarse grained and pulse electrodeposited nanocrystalline nickel samples. The samples will be charged with hydrogen in a newly designed electrochemical cell. The incorporation of the cell into an AFM, enables us to study the impacts of i) type of GBs (e.g. tilt or twist), ii) segregations at the GBs, iii) pile-up of dislocations at the GBs and iv) grain sizes, on the local hydrogen content and hydrogen diffusion rate. In-situ nanoindentation measurements will be performed in order to evaluate the relationship between hydrogen content with local mechanical properties. Studying the contributions of applied external uniaxial tensile stress on the plasticity of a defined GB will be another subject of this work. Moreover, the influence of segregations at the GBs on work hardening and deformation processes in addition to their impact on the local hydrogen concentration will be evaluated.

氢在金属中的存在经常导致断裂模式从韧性穿晶向韧性较低或脆性沿晶的变化。为了理解氢致降解的作用和机制，有必要知道晶粒内的局部氢浓度，特别是在材料不均匀性如晶界（GB）处。在这个项目中，基于AFM的扫描开尔文探针力显微镜（SKPFM）将用于研究局部氢分布在粗晶粒和脉冲电沉积纳米晶镍样品。样品将在新设计的电化学电池中充入氢气。将电池并入AFM中，使我们能够研究i）GB类型（例如倾斜或扭曲），ii）GB处的偏析，iii）GB处的位错堆积和iv）晶粒尺寸对局部氢含量和氢扩散速率的影响。将进行原位纳米压痕测量，以评估氢含量与局部机械性能之间的关系。研究外加单轴拉应力对GB塑性的贡献将是本工作的另一个主题。此外，除了对局部氢浓度的影响之外，还将评估GB处的偏析对加工硬化和变形过程的影响。