Electron energy-loss spectroscopy and first-principles calculation studies on a Ni–Ti shape memory alloy

✍ Scribed by Zhiqing Yang; Wim Tirry; Dirk Lamoen; Svetlana Kulkova; Dominique Schryvers

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 589 KB
• Volume: 56
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2007.10.001

✦ Synopsis

Electron energy-loss spectroscopy (EELS) investigations and first-principles calculations were carried out on different aspects of a Ni-Ti shape memory alloy. The composition of lens-shaped precipitates is determined to be Ni 4 Ti 3 by model-based EELS quantification and the Ni-depleted zone in the B2 matrix surrounding those precipitates is quantified. EELS spectra show that the intensity of the normalized Ni L 3 peak of both the Ni 4 Ti 3 precipitates and Ni-depleted zones is higher than that of matrix regions with the nominal composition, which is confirmed by first-principles simulations. The total amounts of 3d electrons, however, are the same for both elements in the different Ni-Ti structures and regions. The Young's and bulk moduli of the B2 matrix with 51 at.% Ni and the Ni 4 Ti 3 precipitates were evaluated and the precipitates are found to be harder than the matrix, while first-principles calculations indicate that the bulk modulus for the Ni 4 Ti 3 precipitate is higher by 5% than that for the equiatomic NiTi B2 phase.