Effect of Sc, Hf, and Yb Additions on Superplasticity of a Fine-Grained Al-0.4%Zr Alloy

This research was undertaken to study the way deformation behaves in ultrafine-grained (UFG)-conducting Al-Zr alloys doped with Sc, Hf, and Yb. All all, eight were studied zirconium partially replaced by and/or Doping elements (X = Zr, Yb) totaled 0.4 wt.%. The choice of doping conditioned possible precipitation Al3X particles L12 structure course annealing these alloys. Such provide higher thermal stability a nonequilibrium UFG microstructure. Initial coarse-grained samples obtained induction casting. A microstructure formed equal-channel angular pressing (ECAP) at 225 °C. Superplasticity tests carried out temperatures ranging from 300 500 °C strain rates varying between 3.3 × 10?4 10?1 s?1. highest values elongation failure are observed Sc-doped Al-0.2%Zr-0.1%Sc-0.1%Hf alloy has maximum ductility: 450 rate 10?3 s?1, relative reaches 765%. At onset superplasticity, stress (?)–strain (?) curves characterized stage homogeneous (uniform) long localized plastic flow. dependence (?eq) on test temperature is increasing uniformly, which not case for other alloys, ?eq(T) peaking 350–400 sensitivity coefficient flow m small does exceed 0.26–0.3 400–500 In containing no go down 0.12–0.18 It been suggested that lower driven intensive grain growth pore formation large particles, develop specifically an ingot crystallization stage.