Microstructure and mechanical properties of pure Mg after spiral equal-channel extrusion

One of the severe plastic deformation techniques, elliptical cross-sectioned spiral equal-channel extrusion (ECSEE) was successfully applied to the pure Mg processed at 200 degrees C and the microstructure and properties were studied. The observation shows that the grains are refined to 2.1 mu m after 2-pass deformation. The proportion of high-angle grain boundary increases to 49.4% after 6-pass. The minimum time of grain boundary rotating 30 degrees is about 0.847 ms, and the maximum time is 2.34 ms. TEM observation illustrates the grain morphology evolves from shear bands to recrystallised grains. There was a significant increase in strength to similar to 180 MPa but a decrease in the ductility (similar to 12%) of pure Mg after 6-pass ECSEE. The refinement mechanism is mainly divided into mechanical and physical refinement.