Preparation And Performance Study Of The Magnesium-based Bulk Amorphous Alloys

The amorphous ribbons of Mg₆5Cu₂5Y₁0, Mg₇0Cu₂0Y₁0, Mg₇5Cu₁5Y₁0 and Mg₈0Cu₁0Y₁0 alloys were prepared by vacuum melt spinning method and 2mm diameter rods of Mg₆5Cu₂5-xNi_xY₁0 (x=l,2,3) and Mg₆0-xAl_xCu₃0Y₁0 (x=0.3,0.9,2.1) were also prepared by vacuum copper mold casting method in this paper. The structure, glass forming ability (GFA) and crystallization process while heating were studied by differential scanning calorimeter analysis (DSC/DTA) and X-ray diffraction analysis (XRD) respectively.The values of T_g, T_x, T_l,T_rg and ΔT_X for amorphous ribbons, which are the parameters to describe the glass forming ability for bulk metallic glasses and are expressed only by temperature, were deduced from DSC curves and the ratio of the crystallization heat and melting heat was presented as a new parameter-reduced glass transition enthalpy. DSC quantification analysis showed that this new parameter and old parameters gave consistent results when described the glass forming ability of Mg₈0-xCu_10+xY₁0 amorphous ribbons.It is identified that the width of super cooled region ΔT_x of Mg₆5Cu₂5-xNixY₁0 (x=1,2,3)will be enlarged with little Ni addition and the width will reach as much as 43.30K when x=1. The glass forming ability will be increased with larger Ni addition and will reach up to 0.5892 when x=3. It indicates that a proper amount of Ni substituting Cu in the alloy will increase the glass forming ability but decrease the thermal stability. The glass forming ability of Mg₆0-xAl_xCu₃0Y₁0 (x=0.3, 0.9, 2.1) bulk amorphous alloy will decrease while Al substituting Mg and the thermal stability and GFA of the amorphous alloy decreased at the same time.Crystallization process of Mg₆5Cu₂5_xNi_xY₁0 (x=l, 2, 3) alloy was studied when heating by use of Kissinger equation. The results show that the dynamics effect exists in the glass transformation and crystallization process. The influence of activation energy and frequency factor on glass forming ability was studied and the results showed that the glass forming ability increased with less activation energy and frequency factor. When describing the glass forming ability of Mg₆5Cu₂2Ni₃Y₁0, activation energy and frequency factor gave consistent results with reduced glass transformation temperature.