Strengthening Precipitate, Thermal Stability, and Mechanical Properties of Melt-Spun Mg-8Gd-3Nd Alloy

Ribbons of melt-spun Mg-8Gd-3Nd (wt.%) alloy with different circumferential velocities ranging from 20 to 40 m/s were prepared. The phase composition and transformation were studied using x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The ribbon of 40 m/s exhibited two exothermic peaks in the temperature range from 600 to 850 K, which corresponded to some metastable phases. The first phase transformation at 673 K was related to β′-Mg12 (Gd, Nd) precipitate and the other exothermic peak at 833 K was associated with β-Mg5 (Gd, Nd) phase. The improvements of microhardness and tensile properties were ascribed to the coexistence of both β′-Mg12 (Gd, Nd) and β-Mg5 (Gd, Nd) precipitates. Meanwhile, the fine and homogenous β-Mg5 (Gd, Nd) precipitate played a more important role in enhancing mechanical properties compared to β′-Mg12 (Gd, Nd), owing to higher hardness and thermal stability.