Secondary phases in quasicrystal-reinforced Mg-3.5Zn-0.6Gd Mg alloy

The secondary phases in quasicrystal-reinforced Mg-Zn-Gd alloys are investigated by transmission electron microscopy. The orientation relationships between the dendritic I-phase and the Mg matrix are identified to be [1 1 (2) over bar 0](Mg)parallel to[2-fold](I-phase) and (0001)(Mg)parallel to(5-fold)(I-phase). We also find that the dendritic I-phase is brittle along 2-fold, 5-fold, and 3-fold atomic planes during hot extrusion. Moreover, new orientation relations [(1) over bar 101](Mg)parallel to[mirror 2-fold](I-phase) and (0 (1) over bar 1 1)(Mg)parallel to(5-fold)(I-phase) are found between nanoscale I-phase and Mg matrix. The findings have implications for our understanding of excellent mechanical properties of the I-phase-strengthened Mg alloys. (C) 2015 Elsevier Inc. All rights reserved.