Microstructural evolution in Al–Mg–Sc–Zr alloy during severe plastic deformation and annealing

Abstract

Annealing behavior of Al–Mg–Sc–Zr alloy processed by equal-channel angular pressing (ECAP) at 325 °C to various strains and undergone subsequent cold rolling to ∼80% reduction was investigated. ECAP to strain, e ∼3 formed partially recrystallized structure with ultrafine-grain (UFG) mantle zone along the boundaries of initial grains of ∼25 μm size in as-cast and homogenized condition, whilst ECAP to e ∼8 and 10 resulted in nearly 1 μm grain size, with their volume fractions being 0.7 and 0.9, respectively. These structures after ECAP exhibited sufficient stability, within normal grain growth up to ∼5 μm grain size only during annealing for 1 h in the temperature range of 350–520 °C. However, subsequent to ECAP cold rolling and further annealing at 425 °C and above revealed a distinct effect of prior ECAP. While the materials undergone ECAP to e ∼3 and e ∼8 and having lower UFG fractions revealed quite similar behavior, the material undergone ECAP to e ∼10 (and nearly complete recrystallization at ECAP) exhibited abnormal grain growth. The sources of microstructure evolution at different stages of processing are analyzed along with their effects on hardness at ambient temperature.