Compositional and Microstructural Optimization and Microstructural, Thermal and Mechanical Assessment of NiTi Shape Memory Alloys for Ferroelastic Cooling

用于铁弹性冷却的 NiTi 形状记忆合金的成分和微观结构优化以及微观结构、热学和机械评估

• 批准号: 226934279
• 负责人: Professor Dr.-Ing. Gunther Eggeler
• 金额: --
• 依托单位: Lehrstuhl Werkstoffwissenschaft
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/226934279?language=en
• 关键词: Compositional; Microstructural; Optimization; Thermal; Mechanical

In the last decades, alternative refrigeration methods have increasingly received attention because they provide high efficiencies, and thus can contribute to a more efficient use of resources and lower greenhouse gas emissions. Pseudoelastic NiTi-based shape memory alloys (SMAs) represent a promising class of candidate materials for ferroelastic cooling. During mechanical loading, a stress induced martensitic transformation allows for a reversible deformation of up to 7 %. On unloading, stress-induced martensite transforms back to austenite, and recovers its initial shape. Both, forward and reverse transformations are associated with heat effects, an exothermic heat production when martensite forms on loading and an endothermic reaction when it disappears on unloading. In the present work, we aim at studying and exploiting the endothermic heat effect for cooling. The project has four objectives: First, it aims at characterizing the elementary transformation mechanisms which govern cooling during the back transformation of stress induced martensite (atomistic and microstructural reasons for elastocaloric behavior). Second, a procedure will be developed which allows to quantify the elastocaloric heat effects associated with loading and unloading. Thirdly, an effort will be made to optimize the cooling potential of NiTi based alloys through alloying and through tailoring the microstructure. And finally, functional fatigue, which may well limit the service life of a cyclically operating ferroelastic cooling device, will receive attention.

在过去的几十年里，替代制冷方法越来越受到关注，因为它们提供高效率，从而有助于更有效地利用资源和减少温室气体排放。伪弹性镍基形状记忆合金（SMAs）是一类很有前途的铁弹性冷却候选材料。在机械加载过程中，应力诱导的马氏体相变允许高达7%的可逆变形。卸载后，应力诱导马氏体转变回奥氏体，并恢复其初始形状。正向和反向转变都与热效应有关，当马氏体在加载时形成放热产热，当马氏体在卸载时消失时吸热反应。在本工作中，我们的目的是研究和利用吸热效应的冷却。该项目有四个目标：首先，它旨在描述在应力诱导马氏体反向转变过程中控制冷却的基本转变机制（弹热行为的原子和微观结构原因）。其次，将开发一个程序，该程序允许量化与加载和卸载相关的弹性热效应。第三，通过合金化和定制显微组织来优化NiTi基合金的冷却潜力。最后，功能性疲劳，这可能会限制循环运行的铁弹性冷却装置的使用寿命，将受到关注。