In situ diffraction study on decomposition of Ti2AlN at 1500–1800 °C in vacuum
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NOTICE: this is the author’s version of a work that was accepted for publication in Materials Science and Engineering: A. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Materials Science and Engineering: A, [528, 1, 2010] DOI 10.1016/j.msea.2010.08.012
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The susceptibility of Ti2AlN to thermal dissociation at 1500–1800 °C in high-vacuum has been studied using in situ neutron diffraction. Above 1500 °C, Ti2AlN decomposed to TiNx primarily through the sublimation of aluminium (Al). The kinetics of isothermal phase decomposition at 1550 °C was modelled using a modified Avrami equation. An Avrami exponent (n) of 0.338 was determined, indicative of the highly restricted out-diffusion of Al between the channels of Ti6N octahedra. The characteristics of thermal stability and phase transition in Ti2AlN are discussed. Characterisation of surface compositions and examination of cross-sectional microstructures of decomposed Ti2AlN, using synchrotron radiation diffraction and SEM, respectively, verify the findings of the neutron diffraction; that Ti2AlN decomposes to TiNx at the surface primarily via the sublimation of Al from grain boundaries.
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