<p>This study investigates the deformation behavior and microstructural evolution of an Al–Mg–Mn 5xxx alloy under conditions relevant to high-speed blow forming (HSBF). The alloy was tested between 450 and 520&#xa0;°C at strain rates ranging from 0.001 to 1&#xa0;s⁻¹, following a short-time annealing treatment that produced a fine, fully recrystallized grain structure (4.5–5.6&#xa0;μm). Mechanical testing revealed a pronounced dependence of elongation and flow stress on both temperature and strain rate, with maximum ductility observed at 500&#xa0;°C. At this temperature, grain-boundary sliding (GBS) dominated deformation at low strain rates, whereas solute-drag creep (SDC) constrained ductility at 450&#xa0;°C and diffusion-controlled grain growth reduced formability at 520&#xa0;°C. Notably, significant grain refinement was observed after deformation at 1&#xa0;s⁻¹, indicating active continuous dynamic recrystallization (CDRX). Furthermore, Mn-containing dispersoids enhanced grain-boundary pinning and promoted CDRX, thereby maintaining microstructural stability during high-strain-rate deformation. Overall, these findings provide a practical and cost-effective pathway for tailoring microstructure to enable stable high-strain-rate formability in Al–Mg–Mn alloys, supporting the development of materials suitable for future HSBF applications.</p> Graphical abstract