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 degrees 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. (C) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.