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
Full Text PDF
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