Overview of SIMS-Based Experimental Studies of Tracer Diffusion in Solids and Application to Mg Self-Diffusion

    Authors

    N. S. Kulkarni; R. J. B. Warmack; B. Radhakrishnan; J. L. Hunter; Y. Sohn; K. R. Coffey; G. E. Murch;I. V. Belova

    Comments

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    Abbreviated Journal Title

    J. Phase Equilib. Diffus.

    Keywords

    database; diffusion; isotope; magnesium; self diffusivity; SIMS; tracer; diffusivity; GRAIN-BOUNDARY DIFFUSION; ION MASS-SPECTROMETRY; ALLOYS; MAGNESIUM; KINETICS; SIMULATION; MECHANISM; LATTICE; DICTRA; Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy &; Metallurgical Engineering

    Abstract

    Tracer diffusivities provide the most fundamental information on diffusion in materials, and are the foundation of robust diffusion databases that enable the use of the Onsager phenomenological formalism with no major assumptions. Compared to traditional radiotracer techniques that utilize radioactive isotopes, the secondary ion mass spectrometry (SIMS)-based thin-film technique for tracer diffusion is based on the use of enriched stable isotopes that can be accurately profiled using SIMS. An overview of the thin-film method for tracer diffusion studies using stable isotopes is provided. Experimental procedures and techniques for the measurement of tracer diffusion coefficients are presented for pure magnesium, which presents some unique challenges due to the ease of oxidation. The development of a modified Shewmon-Rhines diffusion capsule for annealing Mg and an ultra-high vacuum system for sputter deposition of Mg isotopes are discussed. Optimized conditions for accurate SIMS depth profiling in polycrystalline Mg are provided. An automated procedure for correction of heat-up and cool-down times during tracer diffusion annealing is discussed. The non-linear fitting of a SIMS depth profile data using the thin-film Gaussian solution to obtain the tracer diffusivity along with the background tracer concentration and tracer film thickness is demonstrated. An Arrhenius fit of the Mg self-diffusion data obtained using the low-temperature SIMS measurements from this study and the high-temperature radiotracer measurements of Shewmon and Rhines (Trans. AIME 250:1021-1025, 1954) was found to be a good representation of both types of diffusion data over a broad range of temperatures between 250 and 627 A degrees C (523 and 900 K).

    Journal Title

    Journal of Phase Equilibria and Diffusion

    Volume

    35

    Issue/Number

    6

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    762

    Last Page

    778

    WOS Identifier

    WOS:000345281500011

    ISSN

    1547-7037

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