FeNiCoTi Shape Memory Alloys (SMAs)
Christos Efstathiou, Prof. Huseyin Sehitoglu
There is significant interest in developing iron-based shape memory alloys for applications requiring high strength, high stiffness combined with good recoverability of strains. The nickel and copper based shape memory alloys have been extensively studied in the past research and have found numerous applications in structures. They exhibit considerably lower strength and lower stiffness compared to iron based alloys. Despite their potential, little emphasis has been placed on Fe- based alloys.
The focus of the research in its second year has been to achieve shape memory strains of the order of 2% accompanied with high strength in an iron-based shape-memory material. Utilizing both electrical resistance measurements, strain measurements and microscopic evidence the reversible transformation from austenite to martensite has been documented. At temperatures below the martensite start temperature 100% recoverability of strain was attained in polycrystalline samples. The transformation stress as a function of temperature was also established and follows the classical thermodynamics description of phase transformations.
- Sehitoglu, H., X. Y. Zhang, T. Kotil, D. Canadinc, Y. Chumlyakov, and H. J. Maier, “Shape Memory Behavior of FeNiCoTi Single and Polycrystals,” Metallurgical and Materials Transactions, 33A, 3661, 2002.
- Sehitoglu, H., I. Karaman, X. Y. Zhang, Y. Chumlyakov, and H. J. Maier, “Deformation of FeNiCoTi Shape Memory Single Crystals,” Scripta Materialia, 44, 779-784, 2001.