Electron microscopy of antiphase domain boundary tubes in deformed ordered alloys

Abstract
Antiphase domain boundary (APB) tubes have been observed in a slightly deformed Fe-30.5 at. % Al alloy in dark field electron microscope images taken in superlattice reflexions. The image contrast theory has been developed and accounts satisfactorily for the nature of the APB tube contrast observed. The contrast theory is used to estimate the heights of the tubes. The widths of the tubes range from 20 to 50 $\overset{\circ}{\mathrm A}\dagger$, and the measured heights are in the range of one to six times the elementary height. Evidence is presented that tubes are generated by the Vidoz & Brown (1962) mechanism and by a mechanism of cross-slip and annihilation of screw superdislocations. The possible effects of tubes on flow stress are discussed.