Effect of the long periodic stacking structure and W-phase on the microstructures and mechanical properties of the Mg-8Gd-xZn-0.4Zr alloys

Microstructures and mechanical properties of the Mg-8Gd-xZn-0.4Zr (x = 0, 1 and 3 wt.%) alloys, in the as-cast condition and the as-extruded condition, have been investigated. The results show that both the 14H long periodic stacking structure and the W-phase coexist together in the cast Zn-containing alloys. The volume fraction of the W-phase increases with increasing the addition of Zn. This phase is the crack source of the fracture. The 6H long periodic stacking structure is observed in the extruded Zn-containing alloys. The Mg-8Gd-1Zn-0.4Zr alloy exhibits the highest elongation, and the value of its elongation is 130% at 300 degrees C due to the refined microstructure. The W-phase plays an important role in improving the mechanical properties via pinning the movement of the grains at elevated temperature. (C) 2009 Elsevier Ltd. All rights reserved.

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