Development of Semi-Solid Processes for Hot Extrusion of Magnesium Alloys

Technological barriers that relate to limited capability of magnesium extrusion technology still exist, especially for the higher alloyed grades. Part of this is associated with the unfavorable crystallographic structure of the magnesium, which is Hexagonal Close Packed (HCP). This work suggests an innovative and novel technology for reducing the production cycle from cast to finished product. A unique Semi-Solid casting system was designed and constructed in order to enable casting of large scale commercial billets having thixotropic properties. These have been further hot extruded via conventional direct extrusion press. It is shown that all essential parameters have improved significantly. These include extrusion temperature reduction (up to 1500C), press pressure reduction, increase of extrusion rate (up to four times), and, enhancement of surface quality. In addition good mechanical properties and corrosion resistance were achieved.