Characterization of planar features in Mg–Y–Zn alloys

The planar features in a Mg–8Y–2Zn–0.6Zr (wt.%) alloy solution-treated at 500 °C for 1 h have been examined using conventional transmission electron microscopy and atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. Three types of planar features are detected in the microstructure. The first type, which was previously reported to be an intrinsic stacking fault I 1 bounded by a Frank partial dislocation, is shown to be the 14H precipitate phase that is associated with Shockley partial dislocations. The second type is also a precipitate phase that has a single unit cell height and is associated with Shockley partial dislocations. The third type of planar feature comprises small ribbon-like stacking faults. These stacking faults are determined as intrinsic I 2 type bounded by two Shockley partial dislocations, which is further confirmed by computer simulation. The stacking fault energy associated with the faults is much smaller than that of pure magnesium.