OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Ta b l e 2 Chemical compositions (at.%) in the AlCoCrFeNi alloy in the as-cast state Т30 Al Cr Fe Co Ni Nb Dendrite core 17.76 16.46 18.61 20.30 24.56 2.40 Dendrite periphery 14.85 21.61 20.75 20.14 21.06 1.59 Solid solution in eutectics 12.09 23.86 22.05 19.78 19.28 2.96 Laves phase 3.80 18.36 21.43 23.66 11.56 21.17 secondary-phase grains or from its increased fraction in interdendritic zones via solid solution precipitation (Fig. 1, a). The XRD analysis confirms that an ordered σ phase forms in the alloy at 900°C. In [32], it was reported that the σ phase precipitated from the disordered solid solution where it was enriched in Cr and Fe in the form of dispersed particles. Our SEM studies reveal that σ-phase particles are distributed throughout the dendrite volume (Fig. 3, b). After heat treatment at 1,000 °C, σ-phase particles are still observed, but in smaller amounts (Fig. 3, c). At 1,100 °C, they completely disappear (Fig. 3, d). The SEM analysis reveals that heat treatment significantly alters the structure of the solid solution within dendrites (Fig. 3). During alloy solidification, the cooling process leads to the spinodal decomposition of the disordered solid solution into a Fe- and Cr-enriched disordered solid solution and an ordered B2 phase enriched in Ni and Al [32]. This decomposition results in the formation of the so-called basket weave a b c d Fig. 3. Microstructure of AlFeNiCoCrNb0.25 alloy in the as-cast state and after heat treatment, obtained using SEM: T30 (a); T900 (b); T1000 (c); T1100 (d)
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