https://pure.tue.nl/ws/files/1715165/620302.pdf

Multiphase diffusion in binary and ternary solid-state systems

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/pdf/the-kirkendall-effect-in-solid-state-diffusion-bmsluhy55u.pdf

The Kirkendall effect in solid state diffusion

The physical metallurgy of Ni -rich Ni–Mo alloys is reviewed. Three ordered intermetallic compounds can form in this system, which leads to some intriguing microstructures and has significant effects on properties. The understanding of the nature of these phases, how they are formed, and the factors responsible for property changes are summarized; areas needing further research are indicated. The phase relations and transformations in alloys containing approximately 20 at. -%Mo with Fe additions are reviewed, as these serve as the basis for some commercial alloys. The structures and properties of the commercial alloys are also reviewed.

Physical metallurgy of nickel—molybdenum alloys

We investigated the isothermal cross sections through the ternary phase diagrams FeNiMo, FeCoMo and NiCoMo at 1100δC by means of the diffusion couple technique. Essential points of the results were corroborated by an investigation of equilibrated alloys. Use was made of optical, microprobe and X-ray analyses. Characteristics common to the three phase diagrams are the large homogeneity range of the μ phase and the narrowness of the three-phase regions.

https://pure.tue.nl/ws/files/2246659/620293.pdf

Phase relations in the systems Fe-Ni-Mo, Fe-Co-Mo and Ni-Co-Mo at 1100 degrees C

The diffusion couple technique is a unique and powerful experimental method which provides a framework to determine interdiffusion coefficients in solid solution systems and integrated diffusion coefficients for stoichiometric compounds. From simple marker experiments with incremental diffusion couples, information about relative mobilities of species in solid solution and intermetallic phases can be obtained, and tracer diffusion coefficients can be deduced if pertinent thermodynamic data are at hand. The diffusion couple technique is also a valuable approach in phase diagram studies and establishing composition–structure–property relationships in multicomponent systems. The efficiency of the method is very high. Yet, it is not without shortcomings. A number of error sources that may appear when the diffusion couple technique is used as “a research tool” are discussed in detail.

Diffusion Couple Technique: A Research Tool in Materials Science

Experiments are carried out with Ni samples containing different amounts of carbon. The temperature range used is 800 to 1295°. In the beginning of the diffusion process a layer with a two-phase character is formed, for a high carbon content(i.e., 0.4 wt pct) at all temperatures and for a low carbon content (0.06 wt pct) below 1200°. The layer consists of the phases Mo2C and an Ŋ-carbide Mo54Ni30C18. Above 1000° this Ŋ-carbide is present also as a single-phase layer adjacent to this two-phase layer. After an incubation time a layer consisting of another Ŋ-carbide Mo6M6C is formed in the couples; this has a homogeneity range of only 0.5 at. pct Ni. There exists an intricate relationship between the two-phase layer and the layers of the pure Ŋ-carbides. After a very long annealing time at 1200°, σ-MoNi appears as a part of the Mo6Ni6C layer.

G. D. Rieck

Papers

The influence of carbon on the interdiffusion of Mo and Ni