Characterization of Hot-Extruded Mg-Gd-Y-Zn-Zr Alloy Containing a Novel Lamellar Structure and Related High Elevated-Temperature Mechanical Properties

Hot extrusion was introduced to the Mg-10Gd-3Y-1.5Zn-0.5Zr alloy and microstructure evolution, texture configuration and elevated-temperature mechanical properties were investigated. The results show that the LPSO phase network-distributed along grain boundaries in the as-cast and homogenized alloys is broken and elongated after extrusion, and is streamlined along the extrusion direction (ED). After extrusion, a completely recrystallized microstructure with equiaxed grains of similar to 10 mu m is formed. The most notable feature in as-extruded alloy is numerous fine lamellar structures in DRXed grains, which were identified as basal stacking faults (SFs) with nano-spaced by TEM analysis. The < 0001 > //TD texture results in the hard orientation of most grains along ED. The extruded alloy exhibits excellent elevated-temperature mechanical properties (UTS/287 MPa and YS/218 MPa at 300 degrees C; UTS > 200 MPa at 350 degrees C) along ED, which is significantly higher than alloys with similar composition or even higher rare earth content. The high elevated-temperature strength is mainly related to the fiber strengthening effect of streamline-distributed LPSO, the skeleton support effect of numerous SFs with nano spacing, and the texture strengthening effect of hard grain orientation.