Tungsten is one of the candidate structural materials for the divertor in future fusion reactors, at this it will be exposed to very high heat fluxes and erosion. However the inherent brittleness of tungsten at low temperatures and the relatively high brittle to ductile transition temperature constrains its performance.
The main purpose of this work is to improve the ductility of tungsten and do a comprehensive study on tungsten alloys produced by SPD (severe plastic deformation). It has already been found that a significant improvement in fracture toughness can be achieved by applying severe plastic deformation, which is an effective method to produce bulk material with ultra-fine or nanostructured granular microstructure, resulting in unique mechanical properties. The starting material will be deformed by high pressure torsion (HPT), which is one of the existing techniques for SPD.
The knowledge of absolute values and the homogeneity of internal stress and strain distributions is valuable in order to optimize the processes of the nanostructure development in the HPT process. Thus finite element analysis (FEA) is carried out by using a commercial software ABAQUS, the simulation is established on the elasto-plastic model. From the simulation we also designed and evaluated the safety of the die for HPT (Fig. 1).
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| Fig. 1 Sketch of the simulation model |
To investigate the validity of the simulation results experimental studies will be furthermore performed on commercially pure tungsten and tungsten alloys. The influence of process parameters such as strain, strain rate and applied temperature on the structural evolution and material properties will be studied during HPT experiments. The resulting microstructure and the micromechanical properties of the refined tungsten and tungsten alloys will be studied.