Grain Boundary Diffusion in Metals: Recent Developments

Abstract

An overview on recent progress in grain boundary (GB) diffusion study is presented with emphasis on physical phenomena encountered in GB diffusion experiments such as the linear and non-linear segregation effects. Systematic investigations on pure and alloyed poly-and bicrystals gave conclusive information on the solute segregation behavior and allowed to extract the segregation isotherm solely from GB diffusion studies. Recent progress in fundamental understanding of diffusion processes in two-scale materials with two types of short-circuit diffusion paths is discussed on the basis of GB self-diffusion experiments and Monte-Carlo simulations in powder sintered nanocrystalline material.

Phase-field models for simulating physical vapor deposition and grain evolution of isotropic single-phase polycrystalline thin films

“…The model parameters , and s for microstructure evolution in Eqs. (5) and (6) are fixed by the choice of GB feature size, , and the latent heat for phase transformation, L. In this work, = 1 nm as this is a reasonable value for GB thickness in metallic systems [16][17][18][19][20][21][22]. To select a reasonable value for the latent heat, it is recognized that the energetics for microstructure evolution in a metallic system are related to the melting point of the material [4].…”

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

“…Such measurements are typically within the initial part of the type B regime of diffusion as defined by Harrison. [26,32,33] If an effective diffusivity that includes both bulk and grain boundary diffusion contributions is desired (regime A), a smaller grain size sample, e.g., a nanocrystalline sample, is necessary for using the SIMS technique. In comparison, the radiotracer technique directly provides the effective polycrystalline diffusivity in large grained (tens of microns) samples on account of the large sampling volume.…”

“…In comparison, the radiotracer technique directly provides the effective polycrystalline diffusivity in large grained (tens of microns) samples on account of the large sampling volume. [22,33] It is very difficult currently to use the conventional SIMS technique to obtain grain boundary diffusivities using the Harrison regime C because of detection limits, though some applications of Nano-SIMS have recently emerged. [34] However, averaged grain boundary impurity diffusivities can be obtained using the second (tail) part of the Harrison B regime.…”

“…[26,35] In comparison, radiotracer measurements are well suited to measure grain boundary diffusivities both in the B and C kinetic regimes. [21,33] The Atom Probe technique, [36] which is essentially a mass spectrometric technique with atomic scale resolution, is ideal for specific grain boundary diffusivity measurements in regime C. In this work, only bulk tracer diffusion measurements (within the initial portion of regime B) using the SIMS technique in polycrystalline specimens having large grain sizes (hundreds of lm) are considered.…”

Precipitate-induced nonlinearities of diffusion along grain boundaries in Al-based alloys

“…Using different annealing parameters, the fraction and the radii of the precipitates in the vicinity of the grain boundary can be systematically modified. The tracer diffusion method applied in the present study is highly sensitive to the state of the grain boundaries, grain boundary segregation, and grain boundary precipitation [16,17]. Thus, the determined diffusion coefficients represent a probe of a specific grain boundary state at a time scale at which the bulk diffusion of all substitutional elements in Al is frozen and the attained precipitate state is not modified during the measurements.…”