The effects of the point defects on precipitation in NiAlFe alloys

Microalloying effects on the microstructure and kinetics of nanoscale precipitation in Ni–Al–Fe alloy

“…This confirms that fine precipitates appearing as dark regions in superlattice dark field image (Fig. 10(c)) formed using 100 reflection are coherent disordered bcc a-Fe precipitates inside an ordered matrix [21,22,38].…”

Effects of Aging and Co Addition on Martensitic and Magnetic Transitions in Ni–Al–Fe β-based Shape Memory Alloys

“…The magnetic properties were measured by vibrating sample magnetometry (VSM), and the characteristic transition temperature, the martenstitic transition starting temperature (M s ), the martensitic transition finishing temperature (M f ), the reverse transition starting temperature (A s ) and the reverse transition finishing Effects of low temperature aging and the addition of Co on the martensitic and magnetic transitions in the Ni-Al-Fe b (B2-type structure) alloy system were investigated using differential scanning calorimetry, transmission electron microscopy and vibrating sample magnetometry. The martensitic transition temperatures of a Ni 57 Al 25 Fe 18 specimen homogenized at 1 473 K for 1 h were decreased by aging after homogenization, the maximum decrease by aging being observed at 573 K. On the other hand, the substitution of Co or Fe for Ni induced a decrease of the martensitic transition temperatures and an increase of the Curie temperature, while the substitution of Co for Fe resulted in an increase of the martensitic transition and Curie temperatures. Co was thus shown to be an effective element by which both the martensitic and magnetic transition temperatures can be controlled.…”

“…Figure 3(c) shows the SAD pattern of the martensite phase obtained at 83 K, where the crystal structure of the martensite phase of the aged sample can be identified as an 8M structure, although the crystal structure of the martensite phase before aging in the Ni 57 Al 25 Fe 18 alloy annealed at 1 473 K has been reported to be a 2M structure. 13 25,26) Therefore, it is concluded that the very fine dark contrast in the NiAl b matrix shown in Fig. 3(b) resulted from the Fe-rich bcc particles, which had a strong effect on the martensitic transition temperature, the crystal structure of the martensite phase and the thermomagnetization curve shown in Fig.…”

“…13) It has been reported that the introduction of several percents of the g phase with a disordered fcc structure in the b matrix drastically improves the ductility, 13) whose alloys are potential high temperature SMAs. 14) Recently, systematic study of the martensitic and magnetic transition temperatures of Ni 75Ϫx Al 25 Fe x b single-phase alloys 15) has indicated that the martensitic transition temperature decreases and the Curie temperature increases with increasing Fe content. Although b phase alloys with a Fe composition of over 22.3 at% undergo martensitic transition in the ferromagnetic state, the martensitic and magnetic transition temperatures are lower than room temperature, which is not very attractive from a practical point of view.…”

Kinetics of nanoscale precipitation in Ni–Fe–Al alloys: A magnetic monitoring approach

“…To the best of our knowledge, kinetics of such precipitation reactions occurring at the nanoscale has not been examined via magnetic measurements for intermetallic alloys. Therefore, this study will be the first to discuss the kinetic aspects of ␣-phase precipitation in Ni 50 Fe x Al 50−x (x = 20, 25, and 30) alloys by utilizing a non-conventional characterization technique which exploits the ferromagnetic character of the precipitating phase [18]. In the current work, precipitation was monitored by magnetization measurements encompassing both temperature-scan and isothermal experiments with a vibrating sample magnetometer.…”