Long-term self-annealing of copper and aluminium processed by high-pressure torsion

High-pressure torsion (HPT) is recognized as the most effective method for producing ultrafine-grained and even nanocrystalline structures in metallic systems. Although there are many reports on microstructural refinement of pure metals and metallic alloys, several important problems remain unresolved. For example, more information is needed on the homogeneity of the processed microstructure and on the heat release and temperature rise during HPT processing. Recently, there were reports of hardening in HPT-processed pure metals under conditions of self-annealing. This report presents new experimental data on the relaxation processes in HPT copper and aluminium processed at room temperature under loads of 6.0 and 1.0 GPa for zero and one turn. The experimental results were obtained using X-ray diffraction and by measuring the average Vickers microhardness after ageing.