Abstract
Due to the shortcomings existing in the methods of the traditional severe plastic deformation for the production of refined grain material, this paper presents a new extrusion method – continuous variable cross-section direct extrusion (CVCDE), with which interim dies between the billet and the die are added. This method not only shortens the process, but also realizes the integration of material preparation-forming technology. Compared with conventional extrusion, the extrusion with interim dies has a greater effect on the grain refinement and improves the tensile strength. At the same time, the fracture mechanism changes from brittle cleavage to ductile fracture. By the use of CVCDE, the metal flow uniformity is significantly improved and the possibility of the surface crack decreases. The streamline fold defects disappear when two interim dies have been employed. It provides a theoretical basis for the technique of short process extrusion forming so as to manufacture high performance magnesium alloy production.

Key words
microstructure, mechanical properties, continuous variable cross-section direct extrusion (CVCDE), magnesium alloy

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