Abstract
A combination of conventional extrusion (CE) and rotary swaging (RS) was applied to Mg-1Mn-0.5Al-0.5Ca-xZn (x = 0, 0.5) alloys to obtain high-strength Mg alloys. The microstructure and mechanical properties of as-extruded and as-swaged alloys were investigated in this study. Compared to the as-extruded alloys, the strength of as-swaged alloys increased significantly. The edge region of the as-swaged Mg-1Mn-0.5Al-0.5Ca-0.5Zn exhibits excellent comprehensive mechanical properties of the yield strength (YS) of 379 MPa, ultimate tensile strength (UTS) of 400 MPa and fracture elongation (FE) of 10%. The high strength is attributed to fine grains (1.42 μm), higher density of nanoscale spheroidal Al-Mn precipitates and dislocations caused by RS. The microstructure is refined and the unrecrystallized (unDRXed) fractions decrease due to the formation of twins and high frequency of low angle grain boundaries (LAGBs) during RS. Some initial large Al8Mn5 and (Mg, Al)2Ca phases are crushed and dissolved into the matrix, resulting in the formation of more nanoscale dispersive Al-Mn particles. The texture intensity become stronger after RD which is also contribute to the increasing strength.
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