Effects of La and Be on Glass-Forming Ability of Al 84 Co 8 Y 8 Metallic Glass

The influences of Lanthanum (La) and Beryllium (Be) on glass forming ability (GFA) of amorphous Al84Co8Y8 were studied through replacing Y with 2, 4, 6 and 8 at.% La and Be, respectively. To directly compare the GFA of Al84Co8Y8 with different additions of La and Be, the melt-quenched alloys were fabricated by melt-spinning method under different rotating speeds. The amorphous nature of melt-quenched alloys was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results indicate that certain amount of La can promote the GFA of Al84Co8Y8, and the best composition is Al84Co8Y4La4. However, it is found that Be has not distinct influence on the GFA of Al84Co8Y8. In addition, the investigation on thermal stability of amorphous Al84Co8Y8−xLax alloys shows that the thermal stability of amorphous Al84Co8Y8 alloy can be improved by La addition with a peak at the composition Al84Co8Y6La2. It is also found that the crystallization behavior of amorphous Al84Co8Y8 alloy will be changed by the addition of La, in the form of transforming from two-step to three-step crystallization process.