The study of phase transformations in quasicrystalline materials under the influence of various chemical environments is an important task of materials science. Nitriding, i.e. saturation of the surface of a material with nitrogen, can significantly change its structure and properties, opening up new possibilities for the use of quasi-crystals in various fields. This work is devoted to the study of phase transformations occurring in quasi-crystalline AlCuFeB powders during nitriding.
The initial quasicrystalline AlCuFeB powders were obtained by mechanical alloying followed by annealing to form the icosahedral phase. The powders were nitrided in an ammonia atmosphere at different temperatures and holding times. The phase composition and microstructure of the samples were analyzed by X-ray diffraction and scanning electron microscopy.
The results showed that nitriding of quasicrystalline AlCuFeB powders results in the formation of aluminum and iron nitrides. The destruction of the quasicrystalline structure and the formation of new crystalline phases are observed. The temperature and time of nitriding have a significant effect on the phase composition and morphology of the resulting nitride layers. An increase in temperature leads to an increase in the nitriding rate and the formation of thicker nitride layers.
Studying phase transformations during nitriding of quasicrystalline AlCuFeB powders allows controlling the structure and properties of the resulting materials. Modification of the surface of quasi-crystals by nitriding can improve their corrosion resistance, wear resistance and hardness, expanding the scope of their application as protective coatings and functional materials.
The nitriding reaction, which is of great importance, has not yet been applied to aluminum-based quasicrystals. In this paper, we demonstrate that quasicrystalline AlCuFeB particles undergo phase changes during high-temperature annealing in pure nitrogen. A dense nitride layer of considerable thickness is formed on the particle surface, and a decrease in the Al content in the bulk of the material leads to the transformation of the quasicrystalline structure first into a cubic β-phase and then into a monoclinic λ-phase. The rate of this transformation significantly exceeds the oxidation rate.
Author: S. Kenzari, D. Bonina, J. M. Dubois, V. Fournée
Institute: Research Laboratory of Materials and Metallurgy (LSG2M), CNRS-UMR 7584, Parc de Sorupt, Ecole des Mines, 54042 Nancy, France, Institut Jean L’Amour, CNRS-INPL-UHP, School of Mines, Parc Sorupt, 54042 Nancy, France