Since chromium is superior to most materials with regard to the low neutron-induced radioactivity, it is considered as material in fusion technology. Limitations for the structural application in industry are the low ductility at room temperature and a Ductile to Brittle Transition Temperature (DBTT) which lies significantly above room temperature. In the last years intense research has started to produce nanostructured materials by Severe Plastic Deformation (SPD) [1]. Compared with the undeformed materials these materials with grain sizes clearly smaller than 1 µm; are distinguished by an increase in strengths without loosing ductility.

In the present study unirradiated chromium with a purity of 99.97 % (DUCROPUR) has been deformed by High Pressure Torsion (HPT) and Cyclic Channel Die Compression (CCDC) [2–4]. The chemical composition and the mechanical characteristics of the undeformed chromium are given in [4, 5]. This paper is mainly focused on the structural refinement and the thermal stability of the achieved SPD microstructures.