Deformation of nanocrystalline nickel by cold rolling

In the last few years it has become possible to produce reasonable sized metal samples with average grain sizes of less than 100nm. Concomitantly computational power has increased tremendously allowing simulation of processes in such nanocrystalline metals. Due to these new capabilities and the fact that these materials promise at least theoretically enhanced properties the scientific interest in this field has increased. As in every new area usually some discrepancies emerge during early stages of research. This study is focused on the behavior of nanocrystalline metals during plastic deformation. One size effect is that below a certain size regime for energetic reasons only one dislocation can be supported at a time by an individual grain. Work hardening in coarse grained materials is based on dislocation interactions. This raised the question, how these materials deform and whether they work harden or not.; Cold rolling of nanocrystalline electrodeposited Nickel to small, intermediate and large strains has been chosen as the model system to answer this question. An advantage of this choice is that cold deformation by rolling of Nickel has been extensively studied allowing direct comparison with the new findings for nanocrystalline Nickel. As mentioned, the material will be carefully deformed to different amounts of strain, starting with as small a strain as possible. The microstructural changes, such as micro- and macro-texture, changes in the grain boundary character and the distribution thereof, the changes in apparent grain sizes and the amount of strain stored in the microstructure will be carefully monitored by means of XRD and TEM. Microhardness measurements will link the microstructural changes with mechanical property evolution. The results form the property measurements will be correlated to XRD and microstructural analysis. The findings will be compared to plastic deformation behavior of coarse grained Ni. An in depth discussion will be presented.