High-resolution transmission electron microscopic observation of stacking faults in Fe-35 mol%Al alloy with ordered B2 structure

Stacking faults in an Fe-35 mol%Al alloy with the B2 ordered superlattice structure have been investigated by a diffraction contrast method of transmission electron microscopy (TEM). The detailed observation by a phase contrast method of high-resolution transmission electron microscopy (HRTEM) has also been performed on the alloy. Two types of stacking faults were observed by HRTEM. In order to interpret the experimental images, computer simulations of HRTEM images based on different fault models have been carried out. The image simulations reveal that the model of the stacking faults deduced from the diffraction contrast method of TEM (i.e. the displacement vector R=a〈100〉/2) cannot fit one type of the HRTEM images. In the present study, a possible model of the faults (R=(1 - √3)a〈100〉/2) and a mechanism for their production are proposed.