The influence of Nb and Zr on glass-formation ability in the ternary Fe–Nb–B and Fe–Zr–B and quaternary Fe–(Nb,Zr)–B alloy systems

Glass-forming ability (GFA) in relation to microstructure evolution in the ternary Fe–Nb–B and Fe–Zr–B and quaternary Fe–(Nb,Zr)–B systems was systematically studied in a three-dimensional composition space. Through navigating, it was revealed that alloys with the optimum glass-forming ability (GFA) are coupled with composition regions surrounded by competing crystalline phases. Alloys Fe₇₁Nb₆B₂₃, Fe₇₇Zr₄B₁₉, and Fe₇₁(Nb_0.8Zr_0.2)₆B₂₃ were illustrated to be the best glass formers in the ternary Fe–Nb–B and Fe–Zr–B systems and the quaternary Fe–(Nb,Zr)–B system, respectively, with a critical size for amorphous formation up to 2 mm. They were compared with the theoretical predictions on the basis of an efficient dense-packing model, and good agreements were obtained.