Calculation of antiphase boundary energies in intermetallics

A method is presented which allows the configurational energy change of long-range ordered alloys to be evaluated after the successive slip of superpartial dislocations. The long-range order is described by concentration waves, and effective pair interaction parameters determined from diffuse X-ray and neutron scattering measurements on short-range ordered alloys are used in the calculation. The method is applied to determine the antiphase boundary (APB) energies of dissociated superdislocations in different slip systems for intermetallics with L12, B2 and D03 structures. The results mostly agree with the values of APB energies obtained from measurements of the dissociation of superdislocations using the weak-beam technique of transmission electron microscopy. On the basis of the APB energies obtained experimentally and by calculation, the temperature dependence of the critical resolved shear stress is discussed.