Superplasticity of Ultrafine-Grained Al–6% Mg–0.12% Sc–0.10% Zr Alloys with 0.10% Yb, Er, and Hf Additions

The superplastic behavior of ultrafine-grained (UFG) alloys Al–6% Mg–0.12% Sc–0.10% Zr–0.1% X, where X = Yb (alloy 1 (Yb)), Er (alloy 2 (Er)), and Hf (alloy 3 (Hf)), was studied. The objects of comparison were alloys Al–6% Mg–0.12% Sc–0.20% Zr (alloy 4 (Zr)) and Al–6% Mg–0.22% Sc–0.10% Zr (alloy 5 (Sc)). The effect of a simultaneous increase in the flow stress and elongation to failure in the superplasticity mode has been found. The maximum elongation to fracture in UFG alloys 1 (Yb) and 2 (Er) is observed at lower deformation temperatures than in alloys 4 (Zr) and 5 (Sc). The superplastic characteristics of alloy 3 (Hf) exceed those of alloys 4 (Zr) and 5 (Sc) with an increased content of alloying elements (in at %). UFG alloy 1 (Yb) at low temperature (400°С) has good ductility (δ = 910%). The effect of the type and concentration of alloying elements on the deformation behavior and grain growth in UFG alloys Al–6% Mg is analyzed. With the superplasticity of UFG alloys, there is competition between strain-induced grain growth and dynamic recrystallization. It is shown that the fracture of UFG alloys under superplasticity is caused by the formation of pores on large Al3X particles.