Papers by Keyword: Interdiffusion

Abstract: Traditional theories of interdiffusion in solids based on Fick’s first and second laws and Darken’s equations can not describe the relationship between the diffusion fluxes and the diffusion-induced stresses, because the subject matter of the traditional theories is the diffusing atom or atomic flux, not the volume unit within the interdiffusion field. For this reason, it is suggested that the concept of flow point in the interdiffusion field should be constructed to describe the diffusion-induced stresses and the phase growth.

Abstract: In this paper, the current understanding about the relationships between tracer diffusion coefficients, interdiffusion coefficients and d.c. ionic conductivities in metallic alloy and ionic systems is reviewed with emphasis on recent progress. Quasione component systems are analyzed in terms of the Haven Ratio (and tracer and collective correlation factors). Two and three component alloy systems are analyzed in terms of the Darken-Manning equation and vacancy-wind factors (and tracer and collective correlation factors). Ionic systems with two mobile components are analyzed in terms of a corrected Nernst-Planck Equation.

Abstract: In the present study, platinum-iridium alloys (Ir = 15.8, 27.3, 36.1, 100at.%) were electroplated on a nickel-base single crystal superalloy TMS-82+ followed by a diffusion treatment at 1373K for 1 h. Interdiffusion behavior between the Pt-Ir films and substrates was investigated in terms of chemical composition, phase constitution and morphology. X-ray analysis revealed that annealed specimens consisted of several fcc solid solutioned phases with various lattice parameters, together with ordered intermetallic compounds (L12-(Pt,Ni)3Al and B2-(Ir,Ni)Al), due to the inward diffusion of Pt and Ir from the electrodeposited films to the superalloy substrates, and the outward diffusion of solute elements (Ni, Al, Cr, Co) in the superalloy substrates into the films during annealing. The depth concentration analysis indicated that the Pt-36.1Ir film effectively retarded the outward diffusion of solute elements, especially nickel, from the substrate.

Abstract: A diffusion couple study was carried out with Ni-based superalloy / γ’-Ni3Al with or without a Re-based alloy layer. The Re-based alloy containing Re, W, Cr, and Ni was formed on a second generation, single crystal Ni-based superalloy by using electroplating processes to form films of 70at%Re-Ni and Ni-20at%W, followed by Cr-pack cementation at 1573K for 36ks. The superalloy with or without the Re-based alloy layer was bonded to a γ’−Ni3Al alloy in vacuum. Diffusion couples were annealed in an evacuated quartz ampoule at 1423 K for 90 and 360ks. After the 360ks diffusion treatment the Re-based alloy remained sound and suppressed inward Al diffusion from the γ’-Ni3Al, it was further found that outward diffusion of alloying elements from the alloy substrate to the γ’-Ni3Al was also significantly reduced by the Re-based alloy layer.

Abstract: The application of the Danielewski-Holly model of interdiffusion for modelling of selective and concurrent oxidation of multi-component alloys is presented. This model enables prediction of the evolution of components distributions taking into account interdiffusion and the reactions at the boundary, e.g, due to the oxidation/sulphidation processes. The model is subsequently reformulated to the form suitable for numerical calculation. For illustrating its capabilities modelling of the selective oxidation of Ni-Pt alloys is presented. The results are compared with those obtained from Wagner model. Both models give exactly the same results for the longer reaction times. In Wagner model the equilibrium concentration of the elements at the boundary is reached instantly while in this model it changes with time. Consequently the model allows modelling of initial stages of oxidation.

Abstract: A new inverse method is applied for the determination of interdiffusion coefficients in b- NiAl(Pt) and b-NiAl(Pd). The results show that substitution of Pt or Pd to b-NiAl accelerates the diffusion of aluminium. Within the studied composition range and for Al-poor aluminides, the cross coefficients are negligible except for high Pd contents

Abstract: Enhanced intermixing, induced by a laser beam, has been recently observed in amorphous Se/As2S3 and similar multilayers. We report a model, based on the concept of thermal spikes, which can consistently describe experimental observations. The concentration dependence of the light absorption properties causes the photo-stimulated diffusion to be non-linear even when a concentration independent coefficient of thermo-stimulated diffusion is assumed.