Phase separation in Ni-rich Ni–Ti: the metastable states

✍ Scribed by M. Kompatscher; B. Schönfeld; H. Heinrich; G. Kostorz

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 427 KB
• Volume: 51
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(02)00388-9

✦ Synopsis

The microstructure of Ni-11.3 at.% Ti single crystals was investigated after quenching from the solid solution at 1440 K and after ageing at 873 K for various periods of time by using transmission electron microscopy and Xray scattering near fundamental reflections and superstructure reflections of the ordered precipitates. The two-stage decomposition sequence with the initial formation of metastable γЉ precipitates followed by metastable γЈ precipitates as found by small-angle neutron scattering is confirmed. The long-range order parameter of these precipitates is always close to the maximum value achievable at a given composition. The presence of the first metastable state (γЉ) is related to a rearrangement of the precipitates on a macro-lattice in order to minimize the elastic energy due to coherency strains.