Microstructures of an AZ61 wrought magnesium alloy fabricated by a novel SPD process using thermomechanical simulation

Extrusion-shear (ES), a novel severe plastic deformation (SPD) method which includes initial forward extrusion and a subsequent one step shearing process, has been developed to fabricate fine grained AZ61 Mg alloys in a Gleeble 1500D thermomechanical simulator for the first time. The effects of the ES process on the grain refinement of an as cast magnesium alloy were investigated at different extrusion speeds and the microstructures of the as processed billet and rods were investigated at right, central and left positions. It was found that the extrusion force caused by the ES process at 5 mm x s(-1) is about 5 times of that caused at an extrusion speed of 1 mm x s(-1). Besides, the increase of extrusion speed could improve the deformation stress. The ES extrusion causes serve plastic deformation and improves the dynamic recrystallization during the process. The results confirmed that the ES process can be used to refine the grains effectively and to produce serve plastic deformation. The microstructural investigation showed that grain sizes are finer in the bottom parts than in the other parts of the rod.