From cryogenic to elevated temperatures: Mechanical properties and formability of an Al-Mg-Sc-Zr alloy

The microstructural evolution, mechanical properties and formability of an Al-Mg-Sc-Zr alloy under a wide temperature range (-196 °C∼350 °C)were investigated by scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. At cryogenic temperatures, the alloy exhibits simultaneous improvements in strength, ductility and enhanced work hardening capability due to the suppressed dynamic recovery and reduced thermal activation, which promote dislocation accumulation while inhibit cross-slip, thereby improving deformation homogeneity. Conversely, elevated temperatures induce work softening through dynamic recrystallization and dislocation annihilation, significantly increasing ductility but reducing strength. Furthermore, the alloy exhibits superior formability at cryogenic and elevated temperatures, with better formability at cryogenic. At low temperatures, the alloy exhibits a lower yield-to-tensile ratio, higher plastic strain ratio, and greater work hardening exponent compared to room temperature, which improved uniform plastic deformation significantly enhance formability of the alloy. The Portevin-Le Chatelier (PLC) effect is suppressed owing the limited solute diffusion reduce the dynamic strain aging (DSA). At elevated temperatures, the absence of serrated flow, superior plasticity and reduced planar anisotropy further contribute to enhanced formability. The research provides fundamental insights for engineering applications of Al-Mg-Sc-Zr alloys in extreme service environments.