Reduced functional degradation of a magnetic shape memory alloy by aging under stress

减少磁性形状记忆合金因应力老化而导致的功能退化

• 批准号: 259317613
• 负责人: Professor Dr.-Ing. Hans Jürgen Maier
• 金额: --
• 依托单位: Institut für Werkstoffkunde (IW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/259317613?language=en
• 关键词: Reduced; functional; degradation; magnetic; shape

The objective of the research project proposed in cooperation with the Siberian Physical Technical Institute at Tomsk State University is a comprehensive analysis of the functional degradation in a CoNiGa magnetic shape memory alloy. Previous studies on a conventional NiTi shape memory alloy showed that aging of NiTi single crystals under stress can be used to obtain a microstructure that features only certain precipitate variants. This in turn resulted in a substantial improvement in functional fatigue behaviour. Preliminary work already demonstrated that such a tailoring of the microstructure is also feasible in CoNiGa single crystals. This material, however, can also show magnetic field-induced strains, and thus, a drastically higher power density could be realized than possible in conventional NiTi. With respect to the envisaged applications, cyclic stability of the microstructure is the key issue, which has, however, not been studied yet. The hypothesis of the proposed project is that - similar to the conventional NiTi system - a microstructure that features only certain types of precipitate variants, should demonstrate significantly improved functional degradation resistance. In the proposed research, the effect of precipitate variants on both the conventional as well as the magnetic field-induced shape memory effect will be studied. Firstly, the Russian project-partner will analyse the evolution of the precipitate variants that form during stress-assisted aging by transmission electron microscopy. Subsequently, the influence the various microstructures have on the stability of the conventional shape memory effect will be analysed. The German team will use high currents with short pulses to generate high magnetic field strengths (up to 40 kOe). This will allow for a systematic study of the effects that the microstructures with different types of precipitate variants have on the magnetic field-induced shape memory effect. The motivation here is to understand the microstructural conditions that provide for maximum reversible field-induced strains over many cycles. Therefore, the microstructural evolution will be studied in samples that feature different degrees of functional degradation in order to uncover the relevant damage mechanisms. This will also provide for data that can be used later on to develop a validated model that allows for life prediction under conditions relevant for actual service.

与托木斯克州立大学西伯利亚物理技术研究所合作提出的研究项目的目标是全面分析CoNiGa磁性形状记忆合金的功能退化。以往的研究表明，传统的NiTi形状记忆合金的NiTi单晶在应力下的老化，可以用来获得一个微观结构，其特征在于只有某些沉淀变体。这反过来又导致功能性疲劳行为的实质性改善。初步工作已经表明，这种定制的微观结构也是可行的CoNiGa单晶。然而，这种材料也可以表现出磁场诱导的应变，因此，可以实现比传统NiTi更高的功率密度。关于设想的应用，微观结构的循环稳定性是关键问题，然而，尚未研究。提出的项目的假设是，与传统NiTi系统类似，仅具有某些类型沉淀变体的微观结构应显示出显著改善的功能性抗降解性。在拟议的研究中，将研究沉淀变体对常规形状记忆效应和磁场诱导形状记忆效应的影响。首先，俄罗斯项目合作伙伴将通过透射电子显微镜分析应力辅助老化过程中形成的沉淀变体的演变。随后，将分析各种微结构对常规形状记忆效应的稳定性的影响。德国团队将使用短脉冲的高电流来产生高磁场强度（高达40 kOe）。这将允许系统研究具有不同类型的沉淀变体的微结构对磁场诱导的形状记忆效应的影响。这里的动机是要了解的微观结构条件，提供了最大的可逆场致应变在许多周期。因此，将在具有不同程度功能退化的样品中研究微观结构演变，以揭示相关的损伤机制。这也将提供数据，可用于以后开发一个经过验证的模型，允许在与实际服务相关的条件下进行寿命预测。

项目成果

Two-way shape memory effect and thermal cycling stability in Co35Ni35Al30 single crystals by low-temperature martensite ageing

• DOI: 10.1016/j.scriptamat.2018.02.013
• 发表时间: 2018-06
• 期刊: Scripta Materialia
• 影响因子: 6
• 作者: E. Panchenko;A. Eftifeeva;Y. Chumlyakov;G. Gerstein;H. Maier

Magnetic pulse controlled microstructure development in Co49Ni21Ga30 single crystals

• DOI: 10.1080/02670836.2018.1497129
• 发表时间: 2018-07
• 期刊: Materials Science and Technology
• 影响因子: 1.8
• 作者: G. Gerstein;G. Firstov;Y. Chumlyakov;P. Krooss;T. Niendorf;A. Dalinger;H. Maier

Internal pressure as a key thermodynamic factor to obtain high-temperature superelasticity of shape memory alloys

• DOI: 10.1016/j.matlet.2017.09.034
• 发表时间: 2018-01-01
• 期刊: MATERIALS LETTERS
• 影响因子: 3
• 作者: Gerstein, Gregory;L'vov, Victor A.;Maier, Hans J.
• 通讯作者: Maier, Hans J.