A Method for Determining Twins and Corresponding Schmid Factors Based on Electron Diffraction

Determining orientation relationships between different grains or phases via electron diffraction typically requires coincident zone axes, but it is difficult to achieve in most cases due to tilting angle limitations. To address this challenge, a straightforward method for determining the twinning relationship and twin variant in deformed metals is developed by interpreting the selected area electron diffraction (SAED) patterns and corresponding tilt angles in the transmission electron microscope (TEM). The transformation matrix from the sample coordinate system (SCS) to the crystal coordinate system (CCS) is derived to describe the orientation matrix of the observed target. This method is demonstrated by characterizing twins and corresponding Schmid factors in deformed Ti−15Mo alloy even when the zone axes are not coaxial. This method significantly facilitates the determination of multiple orientation relationships and the quantitative analysis of plastic deformation mechanisms in TEM.