  Measurements of the local tetragonality in Fe-C martensite at microstructural
length-scale through pattern matching of electron backscatter diffraction
patterns (EBSPs) and careful calibration of detector geometry are presented. It
is found that the local tetragonality varies within the complex microstructure
by several per cent at largest and that the scatter in the axial ratio is
increased at higher nominal carbon content. At some analysis points the local
crystal structure can be regarded as lower symmetry than simple body centred
tetragonal. A linear relation between the nominal carbon content and averaged
local tetragonality measured by EBSD is also obtained, although the averaged
axial ratio is slightly below that obtained from more classical X-ray
diffraction measurements.
