Daqing Fang

Microstructures and Properties of Melt-Spun and As-Cast Mg-20Gd Binary Alloy

Mg-20Gd(%, mass fraction) samples were prepared using melt-spinning and copper mold casting techniques. Microstructures and properties of the Mg-20Gd were investigated. Results show that the melt-spun ribbon is mainly composed of supersaturated alpha-Mg solid solution phase and the as-east ingot mainly contains alpha-Mg solid solution and Mg5Gd phase. The differential scanning calorimeter (DSC) curve of the ribbon exhibits a small exothermic peak in the temperature range from 630 to 680 K, which indicates that the ribbon contains a metastable phase (amorphous). Tensile strength at room temperature of the melt-spun ribbon and as-cast specimen are 308 and 254 MPa, respectively. The elongations of the two samples are less than 2%. The fracture surfaces demonstrate that the fracture mode of the as-cast Mg-20Gd is a typical cleavage fracture and that of the melt-spun sample is a combination of brittle fracture and ductile fracture.

Microstructure and mechanical properties of extruded Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy

The Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy ingot and sheet were prepared by casting and hot extrusion techniques, and the microstructure, age hardening behavior and mechanical properties were investigated. The results show that the as-cast alloy mainly contains alpha-Mg solid solution and compounds of Mg5RE and Mg24RE5 (RE=Gd, Y and Nd) phases. The grain size is refined after hot extrusion, and the Mg5RE and Mg24RE5 compounds are broken during the extrusion process. The extruded alloy exhibits remarkable age hardening response and excellent mechanical properties in the peak-aging state. The ultimate tensile strength, yield strength and elongation are 310 MPa, 201 MPa and 5.8% at room temperature, and 173 MPa, 133 MPa and 25.0% at 300 degrees C, respectively.