Hydrostatic extrusion (HE) is a plastic forming process which can be used to obtain sever plastic deformation in a single operation. As in the case of equal channel angular pressing (ECAP), torsion under compression (TUC) and multi-step forging (MSF), it can be used to fabricate ultrafinegrained metal structures, which are characterized by excellent mechanical properties.
The aim of the present study was to test the possibility of using hydrostatic extrusion for the fabrication of high strength materials for medical applications. The materials examined were 316LVM steel and pure titanium. The microstructure and mechanical properties of the materials subjected to cold extrusion were analyzed. It has been found that the HE leads to significant refinement of the material microstructure. In 316LVM steel, cold extrusion induces the deformation nanotwins. The change of the microstructure is accompanied by an improvement of the mechanical properties, such as the hardness, microhardness and the yield stress in final products increase by 30 to 50%.
HE of titanium produces a nanometric structure with a grain size of about 90 nm. The ultrafinegrained metal shows excellent strength properties-the yield stress of 1100 MPa, which is more than 200% value of the initial material.