Development of ultra-elastic bulk alloys usable at cryogenitc temperatures: metal seal materials for hydrogen society

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14498
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26040:Structural materials and functional materials-related
• Research Institution: Tohoku University
• Principal Investigator: Xu Sheng 東北大学, 工学研究科, 特任助教 (10907033)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 弾性変形 / 単結晶 / 格子安定性 / 低ヤング率 / マルテンサイト変態 / 超弾性 / 形状記憶合金

Outline of Final Research Achievements

We analyzed the in-situ neutron diffraction experiment results at J-PARC on a Cu-Al-Mn single crystal alloy sample prepared by cyclic heat treatments, which exhibited giant recoverable strain at room temperature. It was found that the origin of this strain is a true elastic deformation, characterized by reversible lattice strain while maintaining the body-centered cubic structure of the parent phase. Furthermore, mechanical tests conducted from room temperature down to an extremely low temperature of 4.2K revealed that under certain stress levels, the alloy exhibits a low Young's modulus and relatively large elastic strain. Under high stress, martensitic transformation was induced, but upon unloading, reverse transformation occurred, resulting in large reversible strain due to pseudoelasticity even at extremely low temperatures. Based on these results, it is inferred that this alloy is promising as a material for cryogenic seals.

Free Research Field

金属工学

Academic Significance and Societal Importance of the Research Achievements

水素社会の実現に向け、安全で信頼性が高く、漏れのない液体水素の輸送・貯蔵技術の開発が求められている。その中でも、液体水素環境に対応できるシール材の開発が重要である。本研究により、極低温でもゴムのような弾性復元力および低ヤング率と高強度を備えたバルク金属材料の開発に成功した。この材料を使用することで、液体水素温度（－253℃）下でも高い信頼性を持ち、再利用可能な弾性変形金属シール材の製作が可能となる。将来的に、液体水素温度での弾性変形金属シール材を実装できれば、水素社会の発展に向けた多大な貢献が期待される。