Point Defects in Nial Alloys under Pressure
نویسنده
چکیده
We investigate the eeect of elevated pressures on the point defect ther-modynamics in NiAl alloys. A particular motivation for this study is due to the expected elimination of structural vacancies on the Al-rich side at high pressure. We employ the density functional theory to compute point defect energies as a function of pressure, which are in turn used as input to the Wagner-Schottky model. We nd that at about 200 kbar a change in the constitutional defect from VNi to AlNi does take place. The extension of the Wagner-Schottky model by introducing elastic interactions between defects leads to the prediction of a qualitatively new phenomenon in the system, namely the appearance of an isostructural phase transition terminated at a critical point. Similar behaviour is expected in some other ordered oo-stoichiometric compounds.
منابع مشابه
Surface stoichiometry and the initial oxidation of NiAl(110).
Selective oxidation of the surface of an ordered alloy requires redistribution of the atomic species in the vicinity of the surface. This process can be understood in terms of the formation and movements of point defects in the compound. On the basis of ab initio density-functional calculation we found both the creation of exchange defects near the NiAl surface and segregation of Ni vacancies t...
متن کاملPoint Defects in B2 Intermetallic Compounds
We are applying perturbed angular correlations (PAC) to study point defects near 111In probes in ordered B2 alloys. Systems studied include NiAl, CoAl, FeAl, CoGa and PdIn Ten different point defect configurations have been observed in annealed, quenched or mechanically-milled samples. The present status of this work is summarized. Systematics of hyperfine interactions of vacancy defects are th...
متن کاملPhysical metallurgy of nickel aluminides
A description of the important physical metallurgy aspects of Ni3Al and NiAl encompassing structure, crystallographic defects, slip systems and phase stability has been presented in this article. The microstructures generated in the two alloys by conventional as well as novel processing techniques have been discussed. The effect of alloying additions on the microstructure has been enumerated. B...
متن کاملMicrostructures and Mechanical Properties of NiAl-(Cr) and TiAl-(Cr) Intermetallic Alloys
The oxidation resistant light weight aluminides: NiAl and TiAl with ordered
متن کامل