Nucleation and Growth in Undercooled Melts of Bulk-Metallic-Glass Forming Zr_(60)Ni_(25)Al_(15) Alloy

摘要

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 Zr_(60)Ni_(25)Al_(15) alloy. For comparison, Zr_(66.7)Ni_(33.3) and Zr_(66.5)Ni_(33.2)Al_(0.3) were also examined Nucleation undercooling in the bulk-metallic-glass forming Zr_(60)Ni_(25)Al_(15) alloy did not depend on the cooling rate (<10~2K/s), and the maximum undercooling observed was approximately 200 K. Recalescence was not observed in the cooling curves of the Zr_(60)Ni_(25)Al_(15), and the Zr_(66.5)Ni_(33.3)Al_(0.3) alloys. The growth velocity of the crystalline phase in the Zr_(60)Ni_(25)Al_(15) alloy was of the order of 10~(-4) m/s even at a undercooling of 100K. In contrast, clear recalescence was always observed in the Zr_(66.7)Ni_(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.