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 Fe-71(Nb0.8Zr0.2)(6)B-23 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.