Network-shaped fine-grained microstructure and high ductility of magnesium alloy fabricated by cyclic extrusion compression

An extraordinary microstructure with mean grain size of 1.77 μm accompanying fine grains of 150 ± 50 nm was obtained for magnesium alloy AZ31 by cyclic extrusion compression (CEC). The ductility improved 2.2 times while yield strength decreased 50 MPa after CEC 7 passes compared with as-extruded alloy. A compound grain-refining mechanism was proposed to explain the microstructure evolution during CEC. Dislocation density, texture and grain-boundary structure were employed to clarify the relationship between microstructure and mechanical properties of AZ31 alloy after CEC.