MEASUREMENTS OF ANTIPHASE BOUNDARY AND COMPLEX STACKING-FAULT ENERGIES IN BINARY AND B-DOPED NI3AL USING TEM

The fourfold dissociation of superdislocations in Ni3Al has been recorded on images that were formed using second-order reflections, and the dissociation distances of the Shockley partial dislocations that bound a complex stacking fault (d(CSF)) have been measured. Comparisons with computer simulated (2g.5g) images highlight the presence of supplementary intensity peaks when d(CSF) is less than 3.0 nm. These simulations also indicate that the distance between the weaker pair of intensity peaks can be used to measure d(CSF) if the experimental observations are corrected for the image shift that occurs during the microscopy. Experimental observations confirm the presence of the supplementary peaks, and measured values of d(CSF) were found to be larger in binary Ni3Al than in the boron-modified alloy. These measured values have been corrected through comparison to image simulations, and the corresponding complex stacking fault and antiphase boundary energies have been calculated using anisotropic elasticity. The results of this study indicate that the antiphase boundary energies are approximately the same for the two alloys but that the complex stacking fault energy is higher in the boron-containing alloy than it is in the binary alloy.