Macro- and Nanomechanical Properties and Strain Rate Sensitivity of Accumulative Roll Bonded and Equal Channel Angular Pressed Ultrafine-Grained Materials

Several processes of severe plastic deformation are suitable for the production of materials with ultrafine‐grained microstructures which are known to exhibit high strength and often good ductility as well as strain rate sensitive behavior. The most promising ones are equal channel angular pressing (ECAP) for bulk material and accumulative roll bonding (ARB) for the production of sheet material. In order to evaluate the influence of the process on these mechanical properties and the strain rate sensitivity, tensile tests, and nanoindentation tests were performed on material produced up to similar effective plastic strains of εARB = 6.4 and εECAP = 6.3. It could be shown that the macroscopic strength is slightly higher for ARB than for ECAP material and vice versa in nanoindentation. Independent of the testing method, the strain rate sensitivities and activation volumes are similar for both materials. Thus, both processes performed up to similar effective plastic strains lead to comparable improvements in the mechanical properties. Additionally it could be shown, that this comparison allows the identification of the dominant deformation mechanism which is responsible for the observed strain rate sensitivity. Significantly increased strain rate sensitivity in UFG metals is commonly observed. It is widely accepted that the enhanced SRS is the key issue for improved ductility of UFG metals. In order to evaluate the influence of the process – ECAP or ARB – and thus the process induced microstructure on the mechanical properties, UFG aluminium of technical purity (Al 99.5) are produced using these methods. For this purpose quite similar total deformation strains of εARB=6.4 and εECAP=6.3 are selected. Both conditions are investigated in terms of their microstructure, mechanical properties, and strain rate sensitivity.