SPD nanostructured Bulk Metals: Part A

Of all the methods used to produce metals with nanograined structures those of "Severe Plastic Deformation - SPD" have proven to be the most promising ones when bulk and porefree materials are required. SPD can produce nanomaterials of very special properties not only exhibiting enhanced strength but also at the saure time having considerable ductility. In particular, this can be achieved by special heat treatments immediately after deformation. The present project is a joined effort of two internationally renowned groups from the Universities of Vienna and Leoben. The project deals with the scientific Background of the special features of SPD metals and focuses an two aims: 1. The investigations of SPD treated pure metals that were started in the preceding projects are continued concentrating an the dependence of mechanical properties and microstructure an hydrostatic pressure, deformation temperature and lattice type. Therefore, mainly the method of "High Pressure Torsion" set up in the preceding project will be used, and the investigations will be extended to solid solutions and alloys with precipitation. It is the aim to identify by metas of electron microscopy and X-ray diffraction the fundamental mechanisms of the deformation induced development of submicro- and nanocrystalline structures and their effects an the mechanical properties. The results will be used to improve the existing models for strengthening of metals during and alter the SPD process. 2. The second aim is to study the effect of thermal treatment an the mechanical properties, the structural features and the thermal stability of SPD produced nanometals. The influence of alloying atoms and precipitates an the response of the microstructure to thermal treatment is to be investigated, and the search for the basic mechanisms of grain structure relaxation will be intensified by insitu experiments. In project A the Vienna group will perform all experiments with X-ray diffraction, including Bragg profile analyses, in-situ deformation studies with synchrotron radiation (for density / arrangement of dislocations and grain size) and wide angle scattering experiments (for intemal stresses & textures). At the same time the group will carry out the investigations by transmission electron microscopy incl. HRTEM & EDX analyses. Furthermore compression and microhardness tests, resistometry and calorimetry studies will be performed. In addition there will be cooperations with groups from Hungary and Switzerland to achieve complementary results.