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Untersuchung des Wasserstoffeinflusses auf die Nukleation und Bewegung von Versetzungen mit einem elektrochemischen nanoindentierenden AFM

使用电化学纳米压痕 AFM 研究氢对位错成核和运动的影响

基本信息

批准号：
46199164
负责人：
Professor Dr. Horst Vehoff
金额：
--
依托单位：
Lehrstuhl für Experimentelle Methodik der Werkstoffwissenschaften
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2007
资助国家：
德国
起止时间：
2006-12-31 至 2013-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/46199164?language=en
关键词：
Untersuchung des Wasserstoffeinflusses auf die

项目摘要

In the first phase of this project the effect of hydrogen on dislocation nucleation was studied with a NI-AFM. For this, a electrochemical three electrode setup was constructed and incorporated into the NI-AFM. The newly developed ECNI-AFM is capable of performing nanoindentation as well as imaging inside electrolytes. This setup was successfully used to study the effect of cathodically charged hydrogen on dislocation nucleation in pure metals and alloys. It was shown that hydrogen reduces the pop-in load by reducing the activation energy for dislocation nucleation. This new method was able to rank the sensitivity of materials to hydrogen embrittlement not only globally but also for the single phases and grains within a microstructure. The activation energy for dislocation nucleation is related to the shear modulus μ, dislocation core radius p and stacking fault energy, which in turn are altered by hydrogen. However, the effect of hydrogen on each of these parameters could not be measured separately. Therefore, in the planned project the same system will be converted to an electrochemical nano compression (ECNC) machine with the help of a flat punch instead of an indenter. The results of this new technique in combination with the ECNI-AFM results should provide the needed additional information to discriminate the effect of hydrogen on each of the above-mentioned parameters, μ, p, and by measuring the shear stress, strain rate sensitivity within defined slip band as well as the slip band nucleation stress in nano-pillars. Smooth specimens should mainly show the effect of surface and sub-surface enrichment on nucleation. Therefore, ECNC test on notched samples and bending tests are planned in order to study the effect of local hydrogen enrichment on notches. The advantage of this technique is, that the globally measured data, as yield stress and stress-strain curves can be directly correlated to local events.

在本项目的第一阶段，用NI-AFM研究了氢对位错成核的影响。为此，构建了电化学三电极装置并将其纳入NI-AFM。新开发的ECNI-AFM能够在电解质内部进行纳米压痕和成像。该装置成功地用于研究带阴极电荷的氢对纯金属和合金中位错成核的影响。结果表明，氢通过降低位错成核的活化能来降低弹出载荷。这种新方法不仅可以对材料的氢脆敏感性进行全局排序，而且可以对微观结构中的单相和晶粒进行排序。位错成核的活化能与剪切模量μ、位错核半径p和层错能有关，而这些又受氢的影响。然而，氢对这些参数的影响不能单独测量。因此，在计划的项目中，同样的系统将被转换为电化学纳米压缩（ECNC）机器，借助平冲床而不是压头。这项新技术的结果结合ECNI-AFM结果将提供必要的额外信息，以区分氢对上述参数μ， p的影响，并通过测量剪切应力，定义滑移带内的应变率灵敏度以及纳米柱的滑移带成核应力。光滑的试样应主要表现为表面和亚表面富集对成核的影响。因此，计划对缺口样品进行ECNC试验和弯曲试验，以研究局部富氢对缺口的影响。该技术的优点是，全局测量数据，如屈服应力和应力-应变曲线，可以直接与局部事件相关联。