Production of Amorphous Cylinder and Sheet of La₅₅Al₂₅Ni₂₀ Alloy by a Metallic Mold Casting Method

A low pressure casting of a La₅₅Al₂₅Ni₂₀ melt into a copper mold was found to bring about an amorphous bulk in cylindrical or sheet form. The maximum diameter of the amorphous cylinder and the maximum thickness of the amorphous sheet with a width of 5.0 mm were about 3.0 and 2.3 mm, respectively. In comparison with the thermal properties of a melt-spun amorphous La₅₅Al₂₅Ni₂₀ ribbon, the amorphous bulks had a higher onset temperature and a smaller heat evolution of irreversible structural relaxation, but there was no distinct difference in glass transition and crystallization behavior. Thus, the amorphous phase produced by casting had a more relaxed atomic configuration as compared with that for the melt-spun ribbon, but there was no difference in the specific heat curves during reheating for both of the samples heated up to the supercooled liquid region. This is believed to be the first evidence that amorphization takes place by casting into a copper mold. The amorphization allows us to reconfirm an extremely large glass-forming capacity of the La-Al-Ni amorphous alloy as previously found by the present authors.