Nucleation and growth in undercooled melts of bulk-metallic-glass forming Zr60Ni25Al15 alloy

A levitation method using alternating and static magnetic fields was used to measure nucleation and growth of the crystalline phases in melts of the bulk-metallic-glass forming Zr60Ni25Al15 alloy. For comparison, Zr66.7Ni33.3 and Zr66.5Ni33.2Al0.3 were also examined. Nucleation undercooling in the bulk-metallic-glass forming Zr60Ni15Al15 alloy did not depend on the cooling rate (< 10(2) K/s), and the maximum undercoofing observed was approximately 200 K. Recalescence was not observed in the cooling curves of the Zr60Ni25Al15 and the Zr66.5Ni33.2Al0.3 alloys. The growth velocity of the crystalline phase in the Zr60Ni25Al15 alloy was of the order of 10(-4) m/s even at a undercooling of 100 K. In contrast, clear recalescence was always observed in the Zr66.7Ni33.3 alloy. The results showed that the addition of At into the Zr-Ni alloy significantly reduced growth velocity of the crystalline phases. The extremely low growth rate in the Zr-Ni-Al system can contribute to the high glass forming ability.