High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

• Main Authors: Olga Yakovtseva, Maria Sitkina, Ahmed O. Mosleh, Anastasia Mikhaylovskaya
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Materials
• Subjects: aluminum alloy; superplasticity; dynamic recrystallization; microstructural study; dislocation structure; precipitate free zone
• Online Access: https://www.mdpi.com/1996-1944/13/9/2098
• ISSN: 1996-1944

Increasing the strain rate at superplastic forming is a challenging technical and economic task of aluminum forming manufacturing. New aluminum sheets exhibiting high strain rate superplasticity at strain rates above 0.01 s⁻¹ are required. This study describes the microstructure and the superplasticity properties of a new high-strength Al-Zn-Mg-based alloy processed by a simple thermomechanical treatment including hot and cold rolling. The new alloy contains Ni to form Al₃Ni coarse particles and minor additions of Zr (0.19 wt.%) and Sc (0.06 wt.%) to form nanoprecipitates of the L1₂-Al₃ (Sc,Zr) phase. The design of chemical and phase compositions of the alloy provides superplasticity with an elongation of 600–800% in a strain rate range of 0.01 to 0.6/s and residual cavitation less than 2%. A mean elongation-to-failure of 400% is observed at an extremely high constant strain rate of 1 s⁻¹. The strain-induced evolution of the grain and dislocation structures as well as the L1₂ precipitates at superplastic deformation is studied. The dynamic recrystallization at superplastic deformation is confirmed. The superplastic flow behavior of the proposed alloy is modeled via a mathematical Arrhenius-type constitutive model and an artificial neural network model. Both models exhibit good predictability at low and high strain rates of superplastic deformation.