Formation Processes of Nanocomposite Strengthening Particles in Rapidly Quenched Al-Sc-Zr Alloys

Authors A.L. Berezina, T.O. Monastyrska, O.A. Molebny, V.K. Nosenko, A.V. Kotko
Affiliations Institute for Metal Physics of the NAS of Ukraine, 36 Vernadsky Blvd., 03680 Kyiv, Ukraine
Issue Volume 4, Year 2012, Number 1
Dates Received 18 October 2011; revised manuscript received 23 February 2012; published online 14 March 2012
Citation A.L. Berezina, T.O. Monastyrska, O.A. Molebny et al. J. Nano-Electron. Phys. 4 No 1, 01006 (2012)
PACS Number(s) 4.70.dg, 81.07.Bc, 81.10.Fg
Keywords Al-Sc, Al-Zr Al-Sc-Zr Alloys, The rapid quenching from the liquid State, Anomalous supersaturated solid solution, Decomposition of anomalously supersaturated solid solution, Nanocomposite Al3Zr/Al3Sc particles.
Annotation Decomposition processes 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 Т = 1000 C and Т = 1400 ºC. The study of the structure of rapidly solidifyed binary Al alloys alloyed with Sc and Zr showed that the crystallization of anomalously supersaturated solid solution (Tquen. = 1400 ºC) or the crystallization with the formation of "fan" structure (Tquen. = 1000 ºC) are possible depending on the quenching temperature of the melt. The decomposition of anomalously supersaturated solid solution is continuous, with the precipitation of nano-sized spherical Al3X (X-Sc, Zr) particles of L12-ordered phase which is isomorphous to matrix. It was found that 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 A13Zr phase. After co-alloying of Al by Sc and Zr a bimodal grained structure was observed for the hypereutectic ternary alloy (Tquen. = 400ºC). Nano-sized grains of 50-60 nm were present on the boundaries of 1-2 µm large-sized grains. TEM 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. Ternary Al-Sc-Zr alloys have significantly higher thermal stability during aging as compared to binary Al-Sc and Al-Zr alloys.

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