Microstructure evolution and mechanical properties in an Fe-17Cr-4Ni-4Cu alloy aged at 475 °C after different aging times were studied. Conventional transmission electron microscopy (TEM) and ...high-resolution electron microscopy (HREM) studies revealed the formation of 9R-structure Cu-rich precipitates and Cr-rich α’ phase by spinodal decomposition in the samples aged at 475 °C after 100–1000 h. The fine Cu-rich precipitates and Cr-rich α’ phase by spinodal decomposition lead to a significant increase in the hardness, together in the early stages (100 h). Continued aging to 500 h leads to increased precipitation of the Cr-rich α’, which provides significant strengthening, reaching maximum hardening, despite the continued loss of hardening by weakening by the Ostwald ripening of the Cu-rich precipitates. Extending the aging time to 1000 h leads to substantial reversed austenite transformation and a large number of ripening -copper precipitates that causes softening. The results of the impact tests showed that the major fracture mode was cleavage and/or quasi-cleavage.
First-principles calculations based on density functional theory (DFT) are used to calculate the structural, elastic and thermodynamic properties of the supersaturated solid-solution AgNi10 alloy, ...applied mainly to electrical contact materials. In this work, for the exchange-correlation energy, the generalized gradient approximation (GGA) functional is used. The calculated structural and electronic properties of supersaturated solid-solution AgNi10 alloys show that the occupation of Ni in the Ag lattice is ordered. All single-crystal elastic stiffness constants of the energetically and mechanically optimized stable AgNi10 model are calculated using the finite strain method and using the Voigt-Reuss-Hill approximation. Various anisotropic indices like the universal anisotropic index, shear anisotropic index, directional dependence of Young’s modulus, bulk modulus and others are calculated to study the elastic anisotropy. The strong anisotropy in the elastic properties of AgNi10 was confirmed. Phonon dispersions were carried out, showing that the AgNi10 crystal has dynamic stability. The Debye temperature is calculated from the elastic data by estimating the average sound velocity in the AgNi10. Furthermore, the vibrational thermodynamic properties (free energy, enthalpy, entropy and heat capacity) of AgNi10 are obtained successfully.
