Quantification of nanocrystallization by means of X-ray line profile analysis

In crystalline materials the structural scale reaches submicron or even nanometer sizes when plastic deformation is sustained up to very high strains, low deformation temperatures and/or extended hydrostatic pressure. In order to find out the mechanisms of crystal fragmentation, X-ray Line Profile Analysis (XPA) can provide a number of important parameters which are not (or only scarcely) available by other methods such as TEM and residual electrical resistivity. These are the density, arrangement and type of dislocations, and the internal stresses which all can be determined even in case of very large strains and high contents of alloying atoms. Extending XPA to profiles at high order diffraction (Multi Reflection Profile Analysis, MXPA) it is possible to carefully separate strain broadening from size broadening. This is particularly important when the nanomaterials reveal grain sizes smaller than 100 nm, when the size broadening gets similarly high than strain broadening from plastic deformation. In dislocated metals, the dislocation contrast has to be taken into account for a correct evaluation of grain size which reduces to the coherently scattering domain size in case of nanocrystallization due to plastic deformation, namely SPD. When using highly intense Synchrotron radiation, a maximum in spatial and even time resolution is reached enabling in-situ measurements during deformation of the parameters quoted.