DETERMINATION OF A MEAN ORIENTATION FROM A CLOUD OF ORIENTATIONS - APPLICATION TO ELECTRON BACKSCATTERING PATTERN MEASUREMENTS

The purpose of this work was to determine the orientations of grains i n polycrystals using electron backscattering patterns (EBSP). In order to lower the degree of statistical uncertainty, the orientation of th e same grain was measured several times. The orientation of the corres ponding grain was assumed to be the mean of the orientations measured. From a theoretical point of view, the way to calculate a mean orienta tion from several orientations was solved on the basis of the properti es of quaternions. The accuracy of the measurements, including the mea n and maximum deviation of the orientations established, could be eval uated. The orientation of alpha plates of Ti-64 products was determine d and it was possible to show that the metallurgical state of the pare nt beta phase prior to the beta-alpha phase transformation is likely t o influence the orientation spread of the variants inherited from the same beta grain, belonging to the same orientation family.