MANDZIEJ Stan Advanced Materials Analysis

Manufacturing of Nano-Structured Alloys by MaxStrain Technique

Manufacturing of ultra-refined nano-grained materials is now a hot issue in materials science. It took scientists almost half-a-century to convince technologists that the Hall-Petch relation can be a guide towards new-generation of materials with superior combination of properties and actually since two decades an explosive boom is observed in development of techniques producing kilogram(s) of nano-structured materials as well as publishing results obtained by these techniques, most of which implemented severe plastic deformation with self-recovery or post-deformation recovery. In the “big-bang” created around this explosion was carefully forgotten that the nano-structured materials in World’s technology exist since ages and these have been used from ancient swords and mediaeval arms till more recent high-carbon martensitic tool steels, medium-tempered spring steels as well as patented near-eutectoidal wires, all together produced annually in many tens thousands of tons. Thus most recently this initial run for manufacturing a kilogram of nano-material was replaced by somewhat better defined challenging tasks, like how to make the nano-structured materials further process-able and then also stable during exploitation, as well as more efforts have been directed towards development of new better compositions for this last purpose. It was very early defined that the ultimate grain refinement of single-phase alloys makes little of sense as it may lead to very fast deterioration of properties or consistency of the material due to dynamic release of energy stored in it. Accordingly efforts were directed onto multi-phase alloys in which dynamic recovery and recrystallization processes could be hampered by precipitation. And for adequate studying of these processes a proper tool was developed – the MaxStrain device combined with Gleeble thermal-mechanical simulator, on application of which this paper will concentrate. In the present paper is given an example of processing Al-6061 grade wrought alloy by the MaxStrain and obtained microstructures, as well as an explanation is provided regarding factors affecting the processing and stability of the nano-grained alloys.