National University of Science and Technology MISIS (Moscow, Russia)

Z. S. Turaeva, Postgraduate Student of the Department of Physical Metallurgy of Non-Ferrous Metals, m1909900@edu.misis.ru
О. А. Yakovtseva, Associate Professor of the Department of Physical Metallurgy of Non-Ferrous Metals, Candidate of Technical Sciences, yakovtseva.oa@misis.ru
А. V. Irzhak, Associate Professor of the Department of Materials Science of Semiconductors and Dielectrics, Candidate of Physical and Mathematical Sciences, airzhak@iptm.ru
N. N. Avksentieva, Senior Lecturer of the Department of Mathematics, avksentieva.nn@misis.ru
А. V. Mikhaylovskaya, Associate Professor of the Department of Physical Metallurgy of Non-Ferrous Metals, Candidate of Technical Sciences, mihaylovskaya@misis.ru

National University of Science and Technology MISIS (Moscow, Russia)¹ ; Skolkovo Institute of Science and Technology (Moscow, Russia)²

Е. S. Statnik, Researcher of the LUCH Particle Accelerator Laboratory¹, Center for Engineering Systems and Sciences, Skoltech², PhD, eugene.statnik@skoltech.ru

The deformation behavior during superplastic flow and the evolution of the bulk and surface microstructure of an AMg4 (AA5083) alloy with an initial grain size of ~5 μm were investigated. The microstructure evolution and the contributions of superplastic deformation mechanisms were compared under different temperature-rate regimes: regime 1 – 460 °C and 1·10^–3 s^–1; regime 2 – 550 °C and 5·10^–3 s–1; regime 3 – 550 °C and 7·10^–4 s^–1. Under the studied conditions, the strain-rate sensitivity coefficient (m) ranged from 0.45 to 0.55, while the elongation to failure varied from approximately 300% to 600%. Regime 2 provided the highest elongation with the lowest residual porosity. During superplastic deformation, the grain size increased along the tensile axis. Analysis of the bulk structure and marker-grid observations on the specimen surface showed that grain elongation was associated with the combined action of diffusion and dislocation creep. Diffusion creep led to the formation of precipitate-free zones on both sides of transverse grain boundaries and to particle accumulation along longitudinal grain boundaries. As a result, juvenile areas covered with aluminum oxide formed on the deformed surface. This process was more pronounced at the subsolidus temperature of 550 °C. The contribution of dislocation slip/climb/glide, which causes for grain elongation, increased at 460 °C. Grain-boundary glide, resulting in grain displacement along the tensile axis, accounted for approximately 25–35% of the total strain and became more significant with decreasing deformation temperature
and rate.
This study was supported by the Russian Science Foundation (RSF), Grant No. 23-79-01155. Part of the experiments involving the Focused Ion Beam (FIB) was carried out at the Shared Research Facilities Center Materials Science and Metallurgy of the National University of Science and Technology MISIS (NUST MISIS).

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