Decomposition Processes in the Anomalous Supersaturated Solid Solution of Binary and Ternary Aluminium Alloys Alloyed with Sc and Zr |
| A.L. Berezina, T.O. Monastyrska, O.A. Molebny, V.K. Nosenko, and A.V. Kotko
Institute for Metal Physics of the NAS of Ukraine, 36 Vernadsky Blvd., 03680 Kyiv, Ukraine |
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| Decomposition of supersaturated solid solution of aluminium alloys alloyed with Sc and Zr have been studied in the work. The binary hypereutectic Al-Sc alloys, hyperperitectic Al-Zr alloys and ternary Al-Sc-Zr alloys were chosen. Alloys were obtained by the melt-spinning. Melts were quenched from temperatures of T = 1000°C and T = 1400°C. The crystallization of anomalously supersaturated solid solution (Tquen. = 1400°C) or the crystallization with the formation of "fan" structure (Tquen. = 1000°C) are possible. The decomposition of anomalously supersaturated solid solution is continuous, with the precipitation of nanosized spherical Al3X (X = Sc, Zr) particles. The loss of thermal stability of Al-Sc alloys is due to the loss of coherence of the strengthening Al3Sc phase. In Al-Zr alloys the loss of strength is due to the formation of a stable tetragonal DO23-ordered Al3Zr phase. After co-alloying of Al by Sc and Zr a bimodal grained structure was observed for the hypereutectic ternary alloy (Tquen. = 1400°C). Nanosized grains of 50-60 nm were present on the boundaries of 1-2 μm large-sized grains. Transmission electron microscopy shows the formation of nanocomposite Al3Zr/-Al3Sc particles. The formation of Al3Zr shell changes the nature of the interfacial fit of the particle with the matrix and slows down the decomposition during the coalescence. |
| DOI: 10.12693/APhysPolA.122.539 PACS numbers: 64.70.dg, 81.07.Bc, 81.10.Fq |