A new severe plastic deformation method: Twist extrusion

One of the most effective methods for obtaining bulk ultrafine-grained materials is severe plastic deformation that is typically done using equal channel angular pressing. In this work we describe and analyze a new method for obtaining severe plastic deformations proposed by the first author. The method is based on direct extrusion and was called "twist extrusion" The main idea of the method is to extrude a prism work piece through a die with a twist channel. The channel cross-section that is orthogonal to the pressing axis, is constant along this axis. In the general case, it is possible to have channels of quite arbitrary cross-section. Several variations of twist extrusion corresponding to known direct extrusion schemes are also possible; for example, twist extrusion in a container with a thin lubrication layer, hydrostatic or hydromechanical twist extrusion. We argue that in some cases twist extrusion has certain advantages. In particular, it allows to obtain not only bulks, but also end products in the form of a prism with an arbitrary cross-section.