次世代形状記憶合金の原子配列と原子の動きの観察に成功～より高性能の合金開発の指針に～

2025-04-25 東北大学

​図1. 熱処理にともなうCu-Al-Mn系形状記憶合金の原子の並びの変化

＜関連情報＞

• https://www.tohoku.ac.jp/japanese/2025/04/press20250425-01-alloy.html
• https://www.tohoku.ac.jp/japanese/newimg/pressimg/tohokuuniv-press20250425_01_alloy.pdf
• https://www.sciencedirect.com/science/article/pii/S0925838825017165

低温時効処理中のCu-Al-Mn形状記憶合金における化学的相互作用： XASおよびDFTによる研究 Chemical interactions in Cu-Al-Mn shape-memory alloy during low-temperature aging treatment: XAS and DFT study

Zheyuan Liang, Kakeru Ninomiya, Hiroshi Akamine, Sumio Kise, Minoru Nishida, Maiko Nishibori
Journal of Alloys and Compounds  Available online: 1 April 2025
DOI:https://doi.org/10.1016/j.jallcom.2025.180158

Highlights

• The Cu-16.5Al-10.6Mn alloy shows an inhomogeneous distribution of elements.
• X-ray Absorption fine structure revealed a two-stage change in local Mn structure during the aging process.
• Antiferromagnetic-ferromagnetic interaction increased after aging, associated with Mn diffusion.
• Mn diffusion drives the ordering transition during aging in Cu-16.5Al-10.6Mn alloy.

Abstract

Low-temperature aging significantly affects the mechanical properties and martensitic transformation temperatures of Cu-Al-Mn (CAM) alloys. In this study, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) were used to investigate the local order changes in a CAM shape-memory alloy during low-temperature aging treatment. The as-quenched CAM alloys were inhomogeneous, in which the average local Mn exhibited an L2₁-like structure and Cu predominantly occupied the first-nearest-neighbor positions around Al. Conversely, the Cu exhibited a D0₃-like local structure. During the 373 K aging treatment, the average local Mn atoms tended to form an L2₁ structure, and the arrangement of Mn atoms changed in two stages: formation of Mn-rich structures and reduction during 423 K aging treatment, whereas no significant change was observed for Al. Using XAS and magnetic measurements, phase separation was detected in the sample treated at 423 K for 120 min. This observation aligns well with the formation energy based on DFT calculations, which explains the transition from disordered to ordered structures during low-temperature aging driven by the aggregation and diffusion of Mn atoms with antipapal spin moments.