Understanding and designing good glass formers in Zr-Al-Co-(Nb) system combining clusters and mixing entropy

Abstract

Bulk alloy compositions in Zr-Al-Co-(Nb) system were understood and designed using our clusters- and mixing entropy-related method. Glass formers in Zr-Al-Co system were regarded as a mixture of Zr-Al and Zr-Co binary clusters with specific ratio. Icosahedral atomic clusters Co-Co3Zr9, Co-Co6Zr6, Al-Al4Zr8 and an Archimedean octahedral anti-prism cluster Al-Al2Zr8 were obtained and used. The coefficients of clusters were designed by mixing entropy. Only four compositions were designed. Among those, alloy with highest GFA was achieved at the composition of Zr53.6Al18.6Co27.8 which enjoyed the same glass forming ability (GFA) as the well-known Zr56Al16Co28 under the same condition. A series of compositions minor alloyed by Nb were further designed and analyzed. The results show that the optimum addition content of Nb could further enhance the GFA. Through the perspective of clusters and mixing entropy, it was assayed qualitatively the origin of enhancing GFA by minor-alloying element, which might help build a foundation for quantitative analysis of minor alloying.