Solids

Superplasticity of ultrafine-grained Al–Mg–Sc–Zr alloys with different Mg, Sc, Zr content

V. N. Chuvil’deev, M. Yu. Gryaznov, S. V. Shotin, A. V. Nokhrin, K. V. Likhnitskiy, Ya. S. Shadrina, M. K. Chegurov, V. I. Kopylov, A. A. Bobrov

National Research Lobachevsky State University of Nizhny Novgorod

Abstract: Effect of magnesium concentration (2.5, 4.0, 6.0 wt.%), the superplasticity of Al–Mg–Sc–Zr aluminum alloys with different Sc/Zr ratios (Sc/Zr = 0.45, 1.0, 2.2) has been studied. The ultrafine-grained (UFG) alloys are obtained by the Equal-Channel Angular Pressing. Superplasticity tests were carried out in the temperature range from 300$^\circ$ to 500$^\circ$C and in the range of strain rates $(\dot{\varepsilon})$ from 3.3 $\Omega$ 10$^{-4}$ to 3.3 $\Omega$ 10$^{-1}$s$^{-1}$. The maximum elongation to failure $(\delta_{\mathrm{max}})$ is reached at $\dot{\varepsilon}$ = 3.3 $\Omega$ 10$^{-2}$s$^{-1}$. At a test temperature of 500$^\circ$C, the maximum elongation to fracture is $\delta_{\mathrm{max}}$ = 1970% (alloy with 2.5% Mg and Sc/Zr = 2.2) and $\delta_{\mathrm{max}}$ = 1750% (alloy with 2.5% Mg and Sc/Zr = 1.0). When fine-grained alloys with a high zirconium content are heated, simultaneous homogeneous precipitation of Al$_3$(Sc,Zr) particles and discontinous precipitation of fan-shaped submicron Al$_3$Zr particles are observed. An increase in the Sc concentration leads to a decrease in the number of Al$_3$Zr particles formed by the discontinous mechanism and to an increase in the number of Al$_3$Sc nanoparticles. An increase in Mg concentration leads to a decrease in the flow stress and El of fine-grained Al–Mg–Sc–Zr alloys. Studies of the microstructure show that strain-induced grain growth develops with superplasticity. The nature of the elongation to failure dependence on the test temperature is determined by the Sc/Zr ratio – in alloys with Sc/Zr $\ge$ 1, an increase in temperature leads to an increase in ductility, and in alloys with Sc/Zr = 0.45, to a decrease in ductility.

Keywords: Al–Mg alloys, scandium, zirconium, superplasticity, grain growth.

Received: 20.11.2024
Revised: 16.05.2025
Accepted: 08.07.2025

DOI: 10.61011/JTF.2025.12.61808.426-24

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