Bulk Approximate Amorphous Alloys in La-Cu-Ni-Co-Al and Nd-Fe-Co-Al Systems by the New Gas Jet Flow Type Electromagnetic Levitation Process

For Rare Earth-Transition Metal-Al with high undercooled liquid formability and glass-forming ability, bulk alloys have been produced with gas jet flow type electromagnetic levitation process, which is a new containerless process. A series of alloys of La80-xCu10Ni5Co5Alx (x=15, 20, 25 at%) were analyzed with respects to the supercooled solidification process, nucleation behavior of a crystalline phase, and the possibility of the formation of bulk amorphous alloys. In addition, the similar studies were carried out for the specimens containing SiC, which is reported to be effective to enlarge undercooling when used in the containerless process. The results show that the addition of SiC suppresses the nucleation of a crystalline phase, and thus, the undercooling (δT) increases in the range of δT=0.22 to 0.28 Tm, where Tm is the melting point. In addition, partially crystallized bulk amorphous alloys with a diameter of 6 mm are obtainable for the alloys with 0.2 mass% SiC addition when they are solidified at approximate cooling rate of 100 K/s. Furthermore, the SiC free alloys of La65Cu10Ni5Co5Al15 and Nd60Fe20Co10Al10 are also obtainable as partially crystallized bulk amorphous alloys.