In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of ∼0.1 to 0.3 μm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value (∼10–20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall–Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process.

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Nanocrystalline materials and coatings

Permeability, solubility and diffusivity of hydrogen isotopes in stainless steels at high gas pressures

Lattice defects dominating hydrogen-related failure of metals

This report may be updated and revised periodically in response to the needs of the technical community; up-to-date versions can be requested from the editors at the address given below or downloaded at http://www.ca.sandia.gov/matlsTechRef/ . The content of this report will also be incorporated into a Sandia National Laboratory report (SAND2008-1163); the most recent version can be obtained from the link above. The success of this reference depends upon feedback from the technical community; please forward your comments, suggestions, criticisms and relevant public-domain data to the authors C. San Marchi (cwsanma@sandia.gov) and/or B.P. Somerday (bpsomer@sandia.gov) at: Sandia National Laboratories Technical Reference on Hydrogen Compatibility of Materials MS-9404 7011 East Ave Livermore CA 94550.

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Technical Reference on Hydrogen Compatibility of Materials

https://www.research.manchester.ac.uk/portal/files/33614877/AM_16_593R.pdf

Hydrogen assisted crack initiation and propagation in a nickel-based superalloy

In the present work, two nickel-iron-chromium-base superalloys, INCONEL718 and GH761, were heat-treated to obtain different microstructures in the alloys. The hydrogen permeability and diffusivity for the two alloys in various conditions were determined using a gaseous-hydrogen permeation technique to examine the influence of microstructures on hydrogen permeation behavior. Measurements were made over the temperature range of 210 °C to 430 °C. It was shown that the dependencies on temperature for hydrogen permeability and diffusivity for the two alloys obeyed the Arrhenius relationship over the test temperature range and that the precipitated strengthening phases hardly affected the hydrogen permeation and diffusion behavior for the INCONEL718 alloy, but the hydrogen permeability and diffusivity in the aged condition were all slightly lower than those in the solution-treated (ST) condition for the GH761 alloy.

Hydrogen permeation behavior in IN718 and GH761 superalloys

In this work, the hydrogen permeation and diffusion in three iron-base superalloys, JBK-75, Incoloy903 and GH35A, were investigated. A gaseous permeation technique was employed to measure the hydrogen permeabilities and diffusivities of specimens with different, heat treatments for a given alloy over the temperature range of 210–430°C. The effects of strengthening phase γ′ on the hydrogen permeation and diffusion in the alloys were examined. The results showed that the dependences of the hydrogen permeabilities and diffusivities in various alloys on the temperature obeyed Arrhenius relationship over the test temperature range and that the hydrogen permeation behavior in these alloys was essentially independent of their heat-treated conditions, i.e. which was not significantly affected by γt precipitates in the alloys. The hydrogen permeation parameters of the iron-base superalloys were approximately consistent with those of the austenitic stainless steels. The hydrogen transport in these alloys with f.c.c. structure was generally controlled only by the lattice diffusion of hydrogen.

W.X. Chen

Papers

Hydrogen permeation behavior in IN718 and GH761 superalloys

Hydrogen permeation and diffusion in iron-base superalloys

Preparation of Al nanoparticles in a controlled environment

Stability in air of ultrafine particles of chromium

Surface state analysis of Fe50Pd50 alloy ultrafine particles