Research Papers - Department of Materials Engineering

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Subject: search.filters.subject.Interdiffusion coefficients

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    Interdiffusion of the platinum-group metals in nickel at elevated temperatures
    (Pergamon, 2003-06-11) Reed, R. C; Karunaratne, M. S. A
    Rates of interdiffusion of the platinum group metals Ir, Pd, Pt, Rh and Ru with nominally pure nickel have been characterised. Interdiffusion coefficients are estimated by analysing the measured diffusion profiles. In the composition range studied (no greater than 10 wt.% of the platinum group metal), the interdiffusion coefficients display little concentration dependence, but the values can differ by an order of magnitude. In order to rationalise the dependence of the interdiffusion coefficient on atomic number, the data are compared with values for other elements which are already in the literature. A systematic trend is observed: elements furthest from the centre of the period display the largest values and elements at the centre the smallest. It appears therefore that the magnitude of the interdiffusion coefficient correlates strongly with the atomic radius of the interdiffusing transition metal species. Our results suggest the existence of a binding energy between the vacancies and the impurity species. We believe that the interdiffusion data are of considerable use to those designing new and novel grades of superalloy for high temperature applications.
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    Interdiffusion in the face-centred cubic phase of the Ni–Re, Ni–Ta and Ni–W systems between 900 and 1300 C
    (Elsevier, 2000-04-15) Karunaratne, M. S. A; Carter, P; Reed, R. C
    In order to deduce the temperature and composition dependence of the interdiffusion coefficient in the nickel-rich end of the Ni–Re, Ni–Ta and Ni–W systems, a number of diffusion couples have been fabricated and heat treated at temperatures between 900°C and 1300°C. The concentration profiles so-obtained have been determined using an electron microprobe. Subsequently, values of the interdiffusion coefficients were determined using a modified form of the Boltzmann–Matano analysis, and these are presented. Only a very weak concentration dependence of the interdiffusion coefficients was found. The results are compared with the very limited data which are available in the literature.