The 1.85 GPa AlSc Bulk Alloy with Abundant Nanoscale Growth Twins

An in situ ultrahigh-strength ductile Al₅₀Sc₅₀ bulk alloy is produced by the copper mold casting method with a composite microstructure of micron-/submicron-sized grains and nanoscale twins. According to the microstructural investigations, hierarchical nanotwinned lamellar AlSc bundles with embedded micron-/submicron-sized Al₂Sc and AlSc₂ are observed. The as-cast alloy displays a unique act of ultrahigh strength of ～1.85 GPa together with pronounced work hardening and a large plasticity of ～14%. Further microstructural investigations on deformed specimens indicate that abundant hierarchical nanotwinned lamellar AlSc bundles are effective to dissipate localization of shear stress or block dislocations from spreading throughout the alloy and hinder the propagation of microcracks formed by local stress transition.