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<p>The present work investigates the range of critical cooling rates required to form icosahedral quasicrystals during the solidification of an Al<sub>90</sub>Cu<sub>4</sub>Fe<sub>2</sub>Cr<sub>4</sub> (%at) alloy. The previous studies on this alloy have shown that icosahedral quasicrystals can form under rapid solidification conditions. Therefore, determining the critical cooling rate necessary for obtaining these phases is essential for selecting appropriate processing techniques to achieve their formation. In this work, over-sprayed particles of an Al<sub>90</sub>Cu<sub>4</sub>Fe<sub>2</sub>Cr<sub>4</sub> (%at) alloy produced by spray-forming were characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on the particles’ diameters, cooling rates were calculated. A large fraction volume of icosahedral quasicrystal (i-QC) with quasi-spherical shape was obtained for particles with diameters inferior to 25&#xa0;μm (cooling rates higher than 2.1 × 10<sup>5</sup>&#xa0;K/s). Microstructural changes, including the suppressing of i-QC phase and the emergence of new phases (Al<sub>2</sub>Cu, Al<sub>13</sub>Cr<sub>2</sub> and Al<sub>13</sub>Fe<sub>4</sub>), were observed due to the decrease in particles’ sizes and consequent increase in the cooling rates. The disappearance of the i-QC characteristic peak in 43.6° (XRD analysis) between 45&#xa0;μm &lt; <i>d</i> &lt; 80&#xa0;μm and 80&#xa0;μm &lt; <i>d</i> &lt; 100&#xa0;μm, associated with SEM images, establishes 2.1 × 10<sup>4</sup>&#xa0;K/s as the critical cooling rate, below which the formation of i-QC does not occur in the Al<sub>90</sub>Cu<sub>4</sub>Fe<sub>2</sub>Cr<sub>4</sub> (%at) alloy.</p>

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Determination of the Critical Cooling Rate for Quasicrystal Formation in a Gas-Atomized Al90Cu4Fe2Cr4 (%at) Alloy

  • 期刊论文

  • 发表日期：

    2025年2月11日

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  • A. V. Rodrigues,
  • P. M. de Souza,
  • G. Zepon,
  • A. P. Carvalho,
  • R. B. Figueiredo,
  • W. Wolf

摘要

The present work investigates the range of critical cooling rates required to form icosahedral quasicrystals during the solidification of an Al90Cu4Fe2Cr4 (%at) alloy. The previous studies on this alloy have shown that icosahedral quasicrystals can form under rapid solidification conditions. Therefore, determining the critical cooling rate necessary for obtaining these phases is essential for selecting appropriate processing techniques to achieve their formation. In this work, over-sprayed particles of an Al90Cu4Fe2Cr4 (%at) alloy produced by spray-forming were characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on the particles’ diameters, cooling rates were calculated. A large fraction volume of icosahedral quasicrystal (i-QC) with quasi-spherical shape was obtained for particles with diameters inferior to 25 μm (cooling rates higher than 2.1 × 105 K/s). Microstructural changes, including the suppressing of i-QC phase and the emergence of new phases (Al2Cu, Al13Cr2 and Al13Fe4), were observed due to the decrease in particles’ sizes and consequent increase in the cooling rates. The disappearance of the i-QC characteristic peak in 43.6° (XRD analysis) between 45 μm < d < 80 μm and 80 μm < d < 100 μm, associated with SEM images, establishes 2.1 × 104 K/s as the critical cooling rate, below which the formation of i-QC does not occur in the Al90Cu4Fe2Cr4 (%at) alloy.