New possibilities for intense plastic deformation of aluminium alloys on a special CEC press J.Richert, M.Richert, M.Mroczkowski AGH University of Science & Technology, al. Mickiewicza 30, 30-059 Kraków, Poland, http://www.agh.edu.pl/ e-mail: J. Richert; jrichert@agh.edu.pl; e-mail: M. Richert; mrichert@uci.agh.edu.pl; e-mail: M. Mroczkowski; mamrocz@uci.agh.edu.pl ABSTRACT: The new machine for deformation of metals and alloys by Cyclic Extrusion Compression method has been presented. The special, 600 kN capacity press was designed and build to deform materials by the CEC way. The press is equipped by microprocessor control system for hydraulic steering and measurement of the forces exerted by tools. The microstructure of AlMgSi (6082) samples deformed by new CEC press showed the nanometric features such as dimension of grains below 100 nm and large disorientation between nanograins. The nanostructure was found after the 24 cycles of the CEC ( = 16). The simulation of plastic flow in CEC process was performed by a DEFORM software. The process has been modelled in relation to the technically pure aluminium and 6082 aluminium alloys deformed with the reduction of sample diameter from 10 to 8.5 mm and next increase from 8.5 to 10 mm in a single CEC cycle. It was found that at suitably selected values of counterforce the tensile circumferential stresses occurred behind the matrix where radial extrusion took place. Increasing the level of hydrostatic pressure it was possible to prevent an increase of the dangerous tensile stresses. Based on the data from numerical simulation of the CEC processes a special diagram has been prepared, which facilitates suitable choice of the counterforce level. Key words: cyclic extrusion compression, counterforce, nanomaterials, ultra-fine grained materials 1. INTRODUCTION The great advantage of the Cyclic Extrusion Compression method is prevention of the initial shape of sample after each deformation cycle [1, 2]. The deformation in CEC is exerted cyclically by exertion of sample from one chamber of the die to the other. At the same time, as the sample is exerted from one chamber, in the inverse chamber it is compressed to its initial shape. By such way the deformation can be proceeds unlimitedly, if the level of the hydrostatic pressure during the deformation is high enough that prevents the sample cracking. The performed investigations shown that the value of hydrostatic pressure should increase with the increase of cumulated deformation and level of sample hardening [3]. The new CEC press ensure proper control and regulation of the value of hydrostatic pressure. It considerably improved the conditions of the material deformation in the CEC processes. The CEC process belongs to the special methods of Severe Plastic Deformations that enable production of nanomaterials and ultra-fine grained materials with the unusual features and properties [1 - 6]. Using the SPD processes it is possible to produce the bulk nanomaterials. They exhibit high level of hardening simultaneously with the good plasticity [2, 7]. It is reported that the grain size obtained in such materials commonly is placed between the 70 to 200 nm. The achieved grain size depends on the kind of deformed material. The microstructure of materials deformed by the SPD processes usually consists partly from the DOI 10.1007/s12289-008-0 - # Springer/ESAFORM 2008 099 8 Int J Mater Form (2008) Suppl 1:479–482