Glass Forming Ability, Magnetic Properties And Microstructure Of Nd_60-xCe_xFe₃₀Al₁₀ Metallic Glasses

Since the first report of successful preparation of metallic glasses by P. Duwez et al. in Caltech, the materials have attracted increasing interests due to their unique mechanical, magnetic, electrical and chemical properties. As one of the important magnetic amorphous materials, RE-Fe (RE = Nd, Pr) metallic glasses with promising magnetic properties were developed by J. J. Croat and have been intensively investigated because of their great significance in material science and their considerable technological promise. Nd-Fe(Co)-Al bulk metallic glasses (BMGs) have shown attractive glass-forming ability (GFA) and high coercivity at room temperature. However, neither distinct glass transition nor supercooled liquid region has been observed in their differential scanning calorimetry (DSC) traces, while the distinct glass transition and wide supercooled liquid region are common features for other BMGs. And the high coercivity of the BMGs is anomalous because of their disordered structure. Moreover, We induce Ce in to Nd-Fe-Al metallic glasses in order to obtain the low T_g because Ce has lower moduli (E = 34 GPa, B = 22 GPa, and G =14 GPa).In our work, Nd_60-xCe_xFe₃₀Al₁₀ (x = 0, 10, 20, 30, 60) ribbons were prepared from the ingots in argon atmosphere by melting spinning. The amorphous phase, glass forming abilities (GFAs) and magnetic abilities of the alloy samples were examined by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and vibrating sample magnetometer (VSM) respectively. XRD results indicated that the ribbons were amorphous. DSC results showed that there was no obvious glass transition in the samples with x = 0, 10, while, the glass transition temperature T_g presented in the sample with x = 20, 30, 60 and decreased with the increase of Ce concentration, especially, the lowest one was 365 K with x = 60. In addition, the crystallization temperature T_x1 and T_x decreased in the whole process that Ce substituted Nd. Thus, the glass forming abilities (â–³T_x = T_x1-T_g) decreased as the Ce concentration increased in the samples with x = 20, 30, 60 and the largest one was 90 K. The VSM results revealed that the saturation magnetization M_s, remanence M_r and coervicity H_c linearly declined with Nd substituted by Ce, and ultimately, the Ce₆₀Fe₃₀Al₁₀ presented paramagnetism at room temperature.Study on Nd_60-xCe_xFe₃₀Al₁₀ amorphous ribbons annealed at different temperatures shows that the amorphous alloys have a stable Nd-rich hexagonal phase and unknown metastable phase precipitation with the rise of temperature. The precipitation of Nd-rich hexagonal phase will bring high hard magnetic. while x = 20 and x =0, The coercive force H_c and remanence M_r of samples annealed at 523 K are 115.64 Oe, 3.499 emu/g and 333.28 Oe, 6.915 emu/g respectively. Hard magnetic decreased accompany with the precipitation of unknown metastable phase as the temperature rises to 643 K. We argue that hard magnetic of anneal sample comes from Nd-rich hexagonal phase. And the sample presents paramagnetism when the sample completely crystallized.