Achieving high strength of as-extruded Mg−Bi−Ca ternary alloy via rotary swaging and subsequent aging process

A Mg−3.2Bi−0.8Ca (BX31, wt.%) ternary alloy with a yield strength of ~358.1 MPa was fabricated by hot extrusion, room-temperature (RT) rotary swaging and subsequent aging treatment. A fine grain structure (~2 μm) and a few secondary phases were observed in the as-extruded alloy, accompanied by a weak non-basal texture. After RT rotary swaging, the average grain size was reduced to ~1 μm via continuous dynamic recrystallization (CDRX). In addition, a large number of residual dislocations piled up within the grain interior, along with the dynamic precipitation of nano-phases. Peak aging occurred rapidly at 448 K for 35 min. After aging, the grain size hardly changed, the density of residual dislocations slightly decreased, and a large number of nano-precipitates were introduced at the dislocation pile-up sites. The grain boundary strengthening, dislocation strengthening and precipitation strengthening co-dominated the strength of the as-aged alloy.