WEB High Pressure Torsion - Taking advantage of shear localization
Severe plastic deformation (SPD) by high pressure torsion (HPT) was recently proposed for structuring and patterning of heterogeneous materials, wherein pattern formation can be on the one hand of purely mechanistic origin (flow pattern, vortex formation) and on the other hand also include phase transformations . After giving a brief introduction into SPD by HPT, this contribution will focus on generation, peculiarities and opportunities of deformation-induced supersaturation and shear band formation during HPT deformation of multiphase materials.
In addition to processing parameters, the resulting microstructure of an HPT deformed multiphase material is governed by many different aspects, especially thermodynamic (occurring phases, heat of mixing) and mechanical (strength, volume percentage, geometry and arrangement of phases/particles) ones. The outcome of the deformation process is manifold: nanocrystalline single phase alloys or multiphase composites, possibly in a supersaturated state. Ordering on a short scale (nm to < 1µm) might take place by subsequent thermal treatments of the as-deformed material. Most importantly, shear localization might take place during deformation. Especially for fcc-fcc systems of medium composition, pronounced shear band formation was found – resulting in shear bands with a supersaturated single phase and finely lamellar fcc1/fcc2 dual phase regions in between . As shear bands are formed continuously during HPT deformation, a shear band network develops – leading to a rotation of the lamellar structure, further resulting in accelerated refinement of the microstructure. As a consequence, deformation induced mixing proceeds faster. The occurrence of shear bands might further increase mechanical properties, e.g. the fracture toughness of the material.
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant No. 757333).
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