In the present work, new possibilities of the X-ray diffraction for investigations of the 17 phase composition, size, shape and volume fraction of particles in ultrafine-grained (UFG) 18 martensitic steel and the Cu-Cr-Zr alloy have been demonstrated. For the first time, the method of 19 X-ray diffraction in the transmission mode was used to identify particles with a volume fraction of 20 less ...