The effects of process parameters on evolutions of thermodynamics and microstructures for composite extrusion of magnesium alloy

H.-J. Hu;

To research the effects of process parameters on evolutions of extrusion force and temperature
rise and microstructures for composite extrusion of magnesium alloy which includes initial
extrusion and shearing process subsequently and is shortened for "ES" in this paper, the ES
extrusion process has been researched by using finite element modeling (FEM) technology. The
rules of temperature rise and the extrusion force varying with process parameters have been
developed. The thermal- mechanical coupling finite element models including the geometric and
FEM models and solution conditions were applied to calculate the effective strain and
temperature and extrusion force during ES extrusion. The maximum temperature rises in the
billets do not increase with billet temperature rising. The temperature of rod surface increased
continuously with development of ES extrusion. The evolutions of extrusion load curve and
effective stress and temperature can be divided into three stages obviously. Extrusion
experiments have been constructed to validate the FEM models with different process
conditions. The simulation results and microstructure observation showed that ES process can
introduce compressive and accumulated shear strain into the magnesium alloy. The ES extrusion
would cause severe plastic deformation and improve the dynamic recrystallization during ES
extrusion. The microstructures show that ES is an efficient and inexpensive grain refinement
method for magnesium alloys.