Microstructure and mechanical properties of AZ31 Mg alloy produced by a new compound extrusion technique

A new extrusion technique, integrated dual-directional extrusion and spiral deformation(DDES), is proposed and successfully applied to AZ31 Mg alloys with no cracks present in the alloys. Combining finite-element analytic, optical microscopy, and X-ray diffraction techniques, it is found that the DDES process may cause cumulative strains of 1.88 in Mg alloy billet. The average grain size of the alloys can be refined from 300 mu m to 3.5 mu m at a temperature of 573 K, and the basal texture is also dramatically weakened from 53.6 to 6.52. These improvements are mainly attributed to dynamic recrystallization induced by heavily accumulated strain at the spiral region. Further compressive tests are carried out on processed AZ31 Mg alloys, and the superior compressive strength and fracture strain can attain 395 MPa and 30.6 %, respectively, rendering this new deformation technique into a promising approach for further governing properties of Mg-based alloys.