Microstructure and Mechanical Properties of Extruded Mg-Zn-Y Alloys with 14H Long Period Ordered Structure

The compositional dependence of mechanical properties and microstructural change of the extruded Mg-Zn-Y alloys has been investigated in the effort to develop a high strength Mg-Zn-Y alloy with long period ordered (LPO) structure. The extruded alloy Mg96Zn2Y2 exhibited a high yield strength of 390 MPa and elongation of 5% at room temperature, and of more than 300 MPa even at the elevated temperature of 473 K. The heat-treated ingot metallurgy (I/M) Mg-Zn-Y alloys containing very small amounts of yttrium and zinc are characterized by a lamellar phase constructed of 2H-Mg and 14H-LPO structures. Extrusion of the Mg-Zn-Y I/M alloys with LPO structure led to refinement of (alpha)-Mg grains and high dispersion of a hard lamellar phase consisting of torn-off 2H-Mg and bent LPO structures with random grain boundaries, resulting in strengthening of the alloys.