SPD Nanostructured Bulk Metals: Part B

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 intemationally renowned groups from the Universities of Vi-enna 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 means of electron microscopy and X-ray diffraction the fundamental mechanisms of the de-formation 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 in-situ experiments. In project B the Leoben group will apply different techniques of SPD to produce the nanometals. Using special techniques of scanning electron and ion microscopes (BSE, OIM, stereo - photogrammetry, and related in- situ deformation tests) the group will analyze the grain structures and misorientations. lt will also carry out all the tension tests for the ductility investigations including special ones with subsize specimens from HPT samples. Slip trace investigations and local hardness measurements by AFM nanoindentation will supply the mechanical tests. There will be cooperations with groups from Russia and Denmark.