Rotary extrusion as a novel severe plastic deformation method for cylindrical tubes

The cylindrical tubular parts of a high-strength magnesium alloy were processed by a novel severe plastic deformation method (rotary extrusion: RE) at the same strain rate and deformed temperature under various revolutions. The effects of this process on the grain refinement and microhardness of the Mg-12Gd-4.5Y-2Zn-0.4Zr alloys were investigated. The results demonstrated that the tube microhardness decreased as the rotary revolutions increased, whereas the matrix and the second phases became significantly homogeneous. The dynamic recrystallization occurred in the RE process. When the temperature and the strain rate were constant, the grains increased in size as the revolutions increased, whereas the dynamic recrystallization refinement and the grain growth were in dynamic competitive relationships.