A New Bulk Deformation Method – Cyclic Extrusion
Cyclic extrusion is a new bulk deformation method. It consists of two steps. In the first step a part of the work piece will be indirectly extruded. In the second step the extruded part will be backwards pressed into the bulk again so that the original shape of the work piece is retained. Similar to ECAP, cyclic extrusion can be repeated many times without shape change. On the other hand, cyclic extrusion can be applied locally on a work piece so that local grain refining or work hardening is possible. Magnesium alloy AZ31 was cyclically extruded at 400 °C with different tools. The grain size was refined from 800 +m to 15 +m. The local grain refining in the surface zone with cyclic extrusion improved the rollability of cast AZ31. Pure aluminium specimens were cyclically extruded up to 2.5 times, which corresponds to a deformation degree of -7. The microstructure changes were examined with EBSD.
Yafang Han et al.
J. Zhang "A New Bulk Deformation Method – Cyclic Extrusion", Materials Science Forum, Vols. 546-549, pp. 2293-2300, 2007