Nucleation and Growth in Undercooled Melts of Bulk-Metallic-Glass Forming Zr₆₀Ni₂₅Al₁₅ Alloy

Abstract

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, Zr_66.7Ni_33.3 and Zr_66.5Ni_33.2Al_0.3 were also examined. Nucleation undercooling in the bulk-metallic-glass forming Zr₆₀Ni₂₅Al₁₅ alloy did not depend on the cooling rate (<10² K/s), and the maximum undercooling observed was approximately 200 K. Recalescence was not observed in the cooling curves of the Zr₆₀Ni₂₅Al₁₅ and the Zr_66.5Ni_33.2Al_0.3 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 Zr_66.7Ni_33.3 alloy. The results showed that the addition of Al 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.