Alloy diffusion

At present the iron-based alloys diffusion saturation by nitrogen is widely used in industry for the increase of strength, hardness, corrosion resistance of metal production. Inexhaustible and unrealized potentialities of nitriding are opened when applying it in combination with cold working [1-3], It is connected with one of important factors, which affects diffusion processes and phase formation and determines surface layer structure, mechanical and corrosion properties, like crystal defects and stresses [4, 5], The topical question in this direction is clarification of mechanisms of interstitial atoms diffusion and phase formation in cold worked iron and iron-based alloys under nitriding. 

Iron-, nickel-based alloys Diffusion bonding 5.41-11.7 800-1150... 

The substitutional binary alloy diffusion illustrated in Fig. 3.3 is discussed in a treatment pioneered by Darken [6] (see also Crank s book [7]). The system has three components, species 1, species 2, and vacancies, and is assumed to be at constant pressure and temperature with sites that can only be created or destroyed at sources (i.e., the system is network constrained except at dislocations or interfaces). The fluxes are obtained from Eqs. 2.21 and 2.32 ... 

W. Schweika, Disordered Alloys Diffuse Scattering and Monte Carlo Simulations, Springer-Verlag, Berlin, 1998. 

In fact, of course, the range of possible surface structures is not limited to monolayers and randomised alloy diffusion. It is expected [108] that several ojmbinations of metals may result in segre tion of entire monolayers, so that the deposited material may exclusively occupy one or more complete subsurface layers, while the substrate material provides a c ing layer. In their calculations for monolayer Ir on Au lll, for exan q)le, Liu et al [100] have determined an energetic preference of 0.47 eV/adatom for Ir to occupy the second layer rather than the fh t, and a further 0.13 eV/adatom for Ir to occupy the third layer rather than the second. The spin-polarisation of the Ir monolayer drops from 1.27 PB/atom at the surfece to 0.78 pa/atom in the second layer, but then rises again to... 

Anonymous, Palladium alloy diffusion process for hydrogen purification. Platinum Metals Rev. 1962, 6 (2), 47—48. 

Darling AS (1963), Thermal and electrolytic palladium alloy diffusion cells. Platinum Met Rev, 7(41), 126-9. 

Keywords refractory metals, electrodeposition, electrodeposition of alloys, diffusion coatings, corrosion resistance, electrode materials. 

Hunter JB. Commercial development of palladium alloy diffusion cells. Platinum Mat Rev 1960 4 130. 

At a given temperature and external oxygen partial ptressure, Nb (critl) and Nb (crit2) are a function of only grain size (d) of the alloy, diffusion coefficients (Dgi, and D(,) and grain boundary width (5) of the alloy. 

Thermodynamics determine when a potentially protective oxide scale is possible but kinetic issues ultimately determine whether or not a continuous layer will form. Without continuity, optimum protective oxide scale formation is not achieved. These kinetic issues include factors such as the rate of growth of other component oxides on the alloy, solubility and diffusivity of oxygen in the alloy, diffusivity of the alloy components, in particular Cr, Be, Al, or Si, and the form and distribution of Cr, Be, Al, or Si in the alloy. These issues will be discussed in detail for the various intermetallics in Sections 6.3-6.10. 

Solid model Model B Metal alloys Diffusion ... 

Because of the relatively high temperatures that are required to establish steady-state creep in metals and alloys, diffusion-controlled mechanisms typically underlie the resulting deformation. Those mechanisms include the simple... 

The possibility to prepare amorphous alloys via charging with hydrogen gas was discussed by Buschow and Beckmans (1979). These authors argued that the disappearance of sharp reflection lines after charging is due to the formation of microcrystalline decomposition products rather than to the formation of amorphous alloys. Diffusion of metal atoms is a step necessary to bring about phase separation after, or better, during charging. The possibility of metal atom diffusion would, however, lead to spontaneous crystallization if the alloys were amorphous. 

Narita et al. proposed a Re-based alloy diffusion barrier coating [71]. This diffusion barrier can effectively suppress the inward diffusion of Al to a single crystal superalloy and outward diffusion of Ta, Ti and Ni from the substrate. 

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