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Effect of Scandium and Chromium on the Structure and Heat Resistance of Alloys Based on γ-TiAl

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Abstract

It is established that microalloying of γ-titanium aluminides with scandium provides an increase in heat resistance, structure refinement and modification, and formation of a dispersion-strengthened structure with a coherent bond between the strengthening and matrix phases. Proceeding from this an improvement might be expected in strength characteristics over a wide temperature range. The effect in scandium consists in changing the ratio of Al:Ti thermodynamic activities in the direction of forming aluminum oxide at the alloy surface during oxidation as a result of the deoxidizing effect of scandium and the formation of fine oxide inclusions. As a result of this aluminum does not form oxides within the alloy. The distribution of elements within the microstructure of γ-Ti ― Al with 5%Cr after oxidation at 900°C for 300 h is studied. It is established that the surface scale layer that forms sometimes contains Cr in addition to Al and O. A diffusion mechanism is suggested for realizing the Cr-effect according to which chromium and aluminum ions participate in place of titanium ions in forming Al2O3 ― Cr2O3 scale at the metal ― air atmosphere interface.

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Authors and Affiliations

  1. Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, ul. Krzhizhanovskogo 3, Kiev 142, 03142, Ukraine

    Valerii E. Oliker

  2. Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, ul. Krzhizhanovskogo 3, Kiev 142, 03142, Ukraine

    Victor I. Trefilov

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  1. Valerii E. Oliker
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  2. Victor I. Trefilov
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Oliker, V.E., Trefilov, V.I. Effect of Scandium and Chromium on the Structure and Heat Resistance of Alloys Based on γ-TiAl. Powder Metallurgy and Metal Ceramics 39, 487–497 (2000). https://doi.org/10.1023/A:1011374724719

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