Interfacial Segregation of Early Transition Metals in Nickel Aluminide

Vacancy Mobility in Nickel Aluminide versus Composition

The fractional concentration of Ni-vacancies in NiAl at high temperature has been determined for compositions between 50 and 53 at.% Ni from measurements using perturbed angular correlation of gamma rays (PAC). The vacancies were detected by quadrupole interactions induced at nearby In/Cd impurity probes present on the Al sublattice in high dilution. One set of measurements was made at high tem...

Equilibrium Defects and Concentrations in Nickel Aluminide

Perturbed angular correlation of gamma rays was applied to determine properties of equilibrium defects in B2 NiAl near the stoichiometric composition. Point defects were detected through quadrupole interactions they induce at In probe atoms on the Al sublattice. Well-resolved signals were observed for probe atoms having zero, one or two Ni-vacancies (VNi) in the first neighbor shell. The fracti...

Segregation of Interstitial Impurities at Grain Boundaries in Transition Metals

The Effects of Beryllium Additions on the Oxidation of Nickel Aluminide and Titanium Aluminide Based Intermetallics

The effects of Be additions on the oxidation behavior of ~-NiAl in moist air at 1000°C and borderline alumina-forming y (TiAI) + Laves Ti-Al-Cr based alloys at 800°C and 1000°C in dry and moist air were investigated. The addition of Be to ~-NiAl suppressed the formation of transient alumina, and resulted in the formation of a protective BeAl20 4 spinel phase. In dry air, the addition of Be to t...

Continuum theory of interfacial segregation

Theoretical work in the field of interfacial segregation is mainly focused on the Gibbsian approach that uses the dividing surface construct. In this article a continuum approach to the problem of interfacial segregation in multicomponent hydrostatically compressed alloys is developed and the segregation at homophase and heterophase interfaces is considered on common grounds. The Gibbs adsorpti...