The antiphase boundary energies of disperse ordered domains for α-CuAl alloys containing 19, 15, 10, or 6.5at%Al were determined by using a theory of strengthening by ordered particles which was suitable for large domain volume fractions. Values of 70, 34, 27 and 20mJ/m2, respectively, were obtained after inferring that the trailing dislocation in a dislocation pair intersected the domains which were already sheared by the leading dislocation. The increase in antiphase boundary energy with increasing aluminium content was interpreted in terms of a corresponding increase in the internal order of the particles. This interpretation agreed with values computed for disordering entropy. Thus a theoretically predicted value of 73.5mJ/m2 was obtained for Cu-19at%Al when the long-range order parameter was assumed to be unity. At this alloy concentration, the resultant value of antiphase boundary energy was also in very good agreement with the value predicted by a computation which considered a pile-up of paired dislocations.

Antiphase Boundary Energies of α-CuAl Ordered Domains. A.Varschavsky, E.Donoso: Materials Science and Engineering A, 1988, 104, 141-7