Hydrostatic extrusion as a method of grain refinement in metallic materials

The paper describes hydrostatic extrusion (HE) as a method of grain refinement of metallic materials down to the nanometric scale. The main features of this method are: (a) large strain, (b) very high strain rates (even greater than 10(4) s(-1)), and (c) deformation homogeneity. HE offers also the opportunity of obtaining bulk materials in a variety of forms (rods and wires of complex cross-sections, small tubes). The study undertaken on 4 materials (aluminium, aluminium alloy, copper and titanium) has shown that significant grain refinement, down to nanometric scale in the case of titanium and aluminium alloy, occurred during HE processing. This grain refinement produces significantly improved mechanical properties. It has been found that HE offers good prospects for the production of nano-structured metals and alloys.