Understanding stress-oxidation interaction on grain boundary failure: in situ microscale crack propagation experiments

了解应力-氧化相互作用对晶界失效的影响：原位微尺度裂纹扩展实验

• 批准号: 418649505
• 负责人: Dr.-Ing. Xufei Fang
• 金额: --
• 依托单位: Werkstoff- und Grenzflächenmechanik (IAM-MMI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418649505?language=en
• 关键词: Understanding; stress; oxidation; interaction; grain

Oxidation-induced failure and stress corrosion cracking (SCC) of engineering materials has been a long-standing issue in material science and engineering application, for instance, energy conversion at elevated temperatures. This project aims to understand the interplay of thermal, mechanical, and environmental factors on the grain boundaries (GBs) in a NiFe binary alloy (Ni-40at.%Fe alloy, fcc, gamma-phase).To achieve this goal, I plan to deform representative GBs in bi-crystal NiFe alloy via micro-cantilever bending and fracture experiments. Various cantilever sizes (size effect), loading rates (diffusion time scale), loading conditions (stress effect), and environments (vacuum and oxidation for comparison) will be considered to investigate the stress-oxidation interaction and the microstructure evolution:1) I study the stress effect on the oxide growth rate by producing micro-cantilevers by quantifying the oxide intrusion length along the GBs with and without mechanical loading in different environments at fixed temperature. I compare the effects of tension and compression within the micro-cantilevers on diffusion and oxide formation, and thus on the micro-cantilever failure.2) I study the diffusion and oxide formation at the evolving crack tip along the GBs by using multiple loading rates and different sample sizes during in situ micromechanical fracture experiments at fixed temperature. New method will further the understanding of crack propagation with oxide formation. 3) I quantify the GB fracture toughness via fracture tests of micro-cantilevers. This fracture toughness is studied in function of the oxide intrusion length that relates to geometry, loading rates, stress states and GB type. Then I determine the most robust GB type with the highest resistance to oxidation and fracture.4) By examining the fractured sample using high resolution scanning electron microscopy and transmission electron microscopy, I can evaluate the mechanisms which govern the oxide-induced fracture: i) oxide induced dynamic embrittlement; ii) fracture induced by stress-aided grain boundary oxidation.Finite element modelling will be used to calculate the oxide intrusion length, stress states, and geometry effect. Experimental results of the fracture toughness are compared to the modeling to validate the simulations and quantify the influence of the oxide. The developed models can be used to improve the material design of oxidation resistant metals.

工程材料的氧化引起的衰竭和应力腐蚀破裂（SCC）一直是材料科学和工程应用中的长期问题，例如，在升高温度下的能量转换。该项目旨在了解Nife二元合金（NI-40AT。％FE合金，FCC，FCC，Gamma-phase）中的热，机械和环境因素（GBS）的相互作用。为了实现这一目标，我计划通过Micro-Crystal Nife Alloy在微型甲基化合物中和fractenter和fractents进行变形GBS gbs gbs。将考虑各种悬臂尺寸（尺寸效应），负载速率（扩散时间尺度），负载条件（压力效应）和环境（用于比较的真空和氧化），以研究应力氧化相互作用和微观结构的演变：1）我研究应为氧化物的固定温度以及氧化物量化的机构在氧化范围内与氧化物量的不同，以及在氧化杂志上的机构对氧化物的生长量的机构进行量子的不同，以及氧化杂志之间的压力效应。我比较了微型委托人内部的张力和压缩对扩散和氧化物形成的影响，从而比较了微抗逆转录剂故障。2）我研究了在现场微力机器实验中，在固定温度下，使用多个加载速率和不同的样品尺寸研究了GBS不断发展的裂纹尖端的扩散和氧化物形成。新方法将进一步了解氧化物形成的裂纹传播。 3）我通过微型委托人的断裂测试量化了GB断裂韧性。研究了这种断裂韧性在与几何形状，加载速率，应力状态和GB类型有关的氧化物侵入长度的功能中进行了研究。然后，我确定了对氧化和骨折最高抗性的最强大的GB类型。4）通过使用高分辨率扫描电子显微镜和透射电子显微镜检查破裂的样品，我可以评估控制氧化物诱导的骨折的机制：I）氧化物诱导的氧化物诱导的动力学介绍； ii）由应激辅助晶界氧化引起的断裂。将使用Finite元素建模来计算氧化物侵入长度，应力状态和几何效应。将断裂韧性的实验结果与验证模拟并量化氧化物的影响进行比较。开发的模型可用于改善抗氧化金属的材料设计。