Diffusion phenomena in shape memory NiTi alloys subjected to severe plastic deformation
Final Report Abstract
In the current project almost all goals were achieved. However, several unexpected results were obtained, too. Among such results were the first precise determination of the diffusional grain boundary width in severely deformed materials and the unambiguous determination of the excess free volume accommodation at grain boundaries during severe deformation. These achievements allowed the first analysis of the underlying diffusion mechanisms of atomic transport in deformation-modified grain boundaries that in fact was provided by a combination of diffusion measurements with substitutionally and interstitionally diffusing solutes. The effect of precipitation on diffusion phenomena in NiTi was investigated, too, and for the first time fundamentally different contributions of coherent and non-coherent particles on grain boundary diffusion kinetics has been established. The influence of severe deformation on microstructure, kinetic and thermodynamic properties of NiTi was examined in detail and the effect of solid-state amorphization during annealing was established and precisely analyzed. The entire amount of results on grain refinement under severe deformation contributed to the development of a new model of the smallest grain size which can be produced by such treatment.
Publications
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Annealing behaviour of nanocrystalline NiTi (50 at% Ni) alloy produced by high-pressure torsion. Philosophical Magazine 91 (2011) 3079-3092
R. Singh, S.V. Divinski, H. Rösner, R.Z. Valiev, G. Wilde
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Diffusion of Ag and Co in ultrafine grained α-Ti deformed by equal channel angular pressing. J Appl Phys 110 (2011) 083514
J. Fiebig, S.V. Divinski, H. Rösner, Y. Estrin, G. Wilde
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Grain boundary diffusion of Fe in ultrafine-grained nanocluster-strengthened ferritic steel. Acta Mater. 59 (2011) 1346-1353
R. Singh, S.V. Divinski, J.H. Schneibel, G. Wilde
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Microstructure evolution in nanocrystalline NiTi alloy produced by HPT. J. Phase Equilibria and Diffusion. 509S (2011) S290 - S293
R. Singh, S.V. Divinski, H. Rösner, R.Z. Valiev, G. Wilde
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On the theoretical limits of microstructure evolution during severe plastic deformation. Philosophical Magazine 91 (2011) 4574-4593
S.V. Divinski, K.A. Padmanabhan, G. Wilde
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Temperature-induced grain boundary transformations as revealed by grain boundary diffusion in B2 NiTi alloy. Intermetallics 61 (2015) 30-37
D. Liu, J. Fiebig, M. Peterlechner, S. Trubel, M. Wegner, Y. Du, Zh. Jin, G. Wilde, S.V. Divinski
